We report the effects of shock compression and release on the structural and magnetic properties of icosahedral Al-Cu-Fe quasicrystals grown via a self-flux method. A 3 kJ projectile impact modulates the quasicrystalline structure by introducing phason strain without inducing a phase transition, at pressures of 13.4 GPa (first shock) and 21.6 GPa (reflected shock). Magnetic moments and negative Curie–Weiss temperatures of this quasicrystal indicate dilute antiferromagnetic ordering. Shock compression enhanced the T = 10 K saturation magnetization, saturation field, and coercive field, suggesting reduced constraint of ideal icosahedral lattice geometry after shock compression. Both pre- and post-shock samples align the easy magnetization direction along the 5-fold axis at high fields, but the shock-compressed sample briefly shifts to a 2-fold axis at 8 T before returning to 5-fold at 9 T. A Fourier expansion retaining harmonics n = 1–6 is needed to correctly describe the angular dependence of the magnetic torque in the broad field range 20 mT–9 T. The emergence of the odd Fourier terms is a unique property of quasicrystalline magnetic anisotropy. The magnitudes of the even terms increased two-fold following shock compression.
", "doi": "10.1016/j.actamat.2026.122177", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2026-06-01", "volume": "311", "pages": "122177" }, { "id": "authors:bd2mb-kpm87", "collection": "authors", "collection_id": "bd2mb-kpm87", "cite_using_url": "https://authors.library.caltech.edu/records/bd2mb-kpm87", "type": "article", "title": "Anharmonic phonons, thermal expansion, and nuclear quantum effects in Zn", "author": [ { "family_name": "Ladygin", "given_name": "V. V.", "orcid": "0000-0002-5697-6956", "clpid": "Ladygin-Vladimir" }, { "family_name": "Knoop", "given_name": "F.", "orcid": "0000-0002-7132-039X" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille" }, { "family_name": "Granroth", "given_name": "G. E.", "orcid": "0000-0002-7583-8778" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The anharmonic behavior of phonons and thermal expansion of hexagonal zinc were studied from 15 to 690 K by inelastic neutron scattering (INS) and ab initio simulations. Phonon spectra were measured for \ud835\udc44-points covering the full Brillouin zone, giving the phonon density of states (DOS) and dispersions along high-symmetry directions. The dispersions were sharp at 15 K, but diffuse intensity was observed at energies above them. The dispersions broadened with temperature \ud835\udc47 and the diffuse intensity became stronger. This diffuse intensity appeared in all INS measurements and simulations, except for classical molecular dynamics at 15 K. The temperature-dependent effective potential (TDEP) method, which included the nuclear quantum effect from zero-point vibrational dynamics, was used to calculate the free energy and thermal expansion. For \ud835\udc47<100K nuclear quantum effects were essential for obtaining the correct negative thermal expansion, and path integral molecular dynamics (PIMD) was particularly effective for obtaining the negative thermal expansion in the basal plane. A Heisenberg-Langevin model for interacting phonons coupled to a thermal bath was able to reproduce the shape and intensity of the diffuse spectral features.
", "doi": "10.1103/pr3j-jwd5", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2025-12-04", "series_number": "12", "volume": "9", "issue": "12", "pages": "125001" }, { "id": "authors:rn19x-kd066", "collection": "authors", "collection_id": "rn19x-kd066", "cite_using_url": "https://authors.library.caltech.edu/records/rn19x-kd066", "type": "article", "title": "Thermodynamic origin of the pressure-induced Invar effect: General criterion and experimental study of Fe\u2086\u2088\u2062Pd\u2083\u2082", "author": [ { "family_name": "Priesen Reis", "given_name": "E. R.", "orcid": "0009-0000-5385-9466", "clpid": "Priesen-Reis-E-R" }, { "family_name": "Guzman", "given_name": "P.", "orcid": "0000-0002-9726-8315", "clpid": "Guzman-Pedro" }, { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-S-H" }, { "family_name": "Lin", "given_name": "A.", "clpid": "Lin-A" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-C-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Zhao", "given_name": "J. Y." }, { "family_name": "Shen", "given_name": "G." }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169" }, { "family_name": "Alp", "given_name": "E. E." }, { "family_name": "Lavina", "given_name": "B.", "orcid": "0000-0002-8556-7916" } ], "abstract": "Synchrotron x-ray diffraction measurements were performed on \u2075\u2077Fe\u2086\u2088\u2062Pd\u2083\u2082 at multiple pressures and two temperatures in a diamond-anvil cell. Between 4 and 11 GPa, the thermal expansion was zero or slightly negative. This pressure-induced Invar effect was studied further with \u2075\u2077Fe nuclear forward scattering and nuclear resonant inelastic x-ray scattering to obtain information on the pressure-induced changes in both the magnetization and the phonon density of states. Magnetic entropy and phonon entropy were obtained from these results, the latter with additional measurements from inelastic neutron scattering to account for the contributions from Pd atoms. The dependencies of these entropies on pressure gave the magnetic and phonon contributions to thermal expansion. These canceled in the region of pressure-induced Invar behavior, even though they individually increased by more than a factor of 2 below the Curie pressure. The behavior of phonons gives evidence for spin-phonon interactions in Fe\u2086\u2088\u2062Pd\u2083\u2082. A general explanation of the pressure-induced Invar effect is presented, showing that Invar behavior is typically expected at a pressure \ud835\udc43* below a magnetic transition at pressure \ud835\udc43C. The difference in pressure \ud835\udc43C−\ud835\udc43* scales with the fractional reduction in magnetic exchange interaction per fractional change in volume, divided by the average Grüneisen parameter.
", "doi": "10.1103/3c95-rf1b", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2025-10-10", "series_number": "14", "volume": "112", "issue": "14", "pages": "144416" }, { "id": "authors:tmyjq-tsm95", "collection": "authors", "collection_id": "tmyjq-tsm95", "cite_using_url": "https://authors.library.caltech.edu/records/tmyjq-tsm95", "type": "article", "title": "High-Energy Density Li-Ion Battery Cathode Using Only Industrial Elements", "author": [ { "family_name": "Patheria", "given_name": "Eshaan S.", "orcid": "0000-0002-2761-8498", "clpid": "Patheria-Eshaan-S" }, { "family_name": "Guzman", "given_name": "Pedro", "orcid": "0000-0002-9726-8315", "clpid": "Guzman-Pedro" }, { "family_name": "Soldner", "given_name": "Leah S.", "orcid": "0009-0009-9355-5761", "clpid": "Soldner-Leah-S" }, { "family_name": "Qian", "given_name": "Michelle D.", "orcid": "0000-0002-4815-1014", "clpid": "Qian-Michelle-D" }, { "family_name": "Morrell", "given_name": "Colin T.", "orcid": "0000-0002-8010-2474", "clpid": "Morrell-Colin-T" }, { "family_name": "Kim", "given_name": "Seong Shik", "orcid": "0000-0003-2604-6392", "clpid": "Kim-Seong-Shik" }, { "family_name": "Hunady", "given_name": "Kyle", "orcid": "0000-0001-8364-786X", "clpid": "Hunady-Kyle" }, { "family_name": "Priesen Reis", "given_name": "Elena R.", "orcid": "0009-0000-5385-9466", "clpid": "Priesen-Reis-Elena-R" }, { "family_name": "Dulock", "given_name": "Nicholas V.", "orcid": "0009-0008-6616-4039", "clpid": "Dulock-Nicholas-V" }, { "family_name": "Neilson", "given_name": "James R.", "orcid": "0000-0001-9282-5752" }, { "family_name": "Nelson Weker", "given_name": "Johanna", "orcid": "0000-0001-6856-3203" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "See", "given_name": "Kimberly A.", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "abstract": "Li-ion batteries are crucial for the global energy transition to renewables; however, their scalability is limited by the supply of key elements used in commercial cathodes (e.g., Ni, Mn, Co, P). Therefore, there is an urgent need for next-generation cathodes composed of widely available and industrially scalable elements. Here, we introduce a Li-rich cathode based on the known material Li2FeS2, composed of low-cost elements (Al, Fe, S) that are globally mined and refined at an industrial scale. The substitution of redox-inactive Al3+ for Fe2+ achieves remarkably high degrees of anion redox, which, in turn, yields high gravimetric capacity (≈450 mAh·g-1) and energy density (\u22731000 Wh·kg-1). We show that Al3+ enables high degrees of delithiation by stabilizing the delithiated state, suppressing phase transformations that would otherwise prevent deep delithiation and extensive anion redox. This mechanistic insight offers new possibilities for developing scalable, next-generation Li-ion battery cathodes to meet pressing societal needs.
", "doi": "10.1021/jacs.4c18440", "issn": "0002-7863", "publisher": "American Chemical Society", "publication": "Journal of the American Chemical Society", "publication_date": "2025-03-19", "series_number": "11", "volume": "147", "issue": "11", "pages": "9786-9799" }, { "id": "authors:vbnzj-e3b82", "collection": "authors", "collection_id": "vbnzj-e3b82", "cite_using_url": "https://authors.library.caltech.edu/records/vbnzj-e3b82", "type": "article", "title": "Diffuse intensity from phonon noise in inelastic neutron scattering", "author": [ { "family_name": "Saunders", "given_name": "Claire N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Ladygin", "given_name": "Vladimir V.", "orcid": "0000-0002-5697-6956", "clpid": "Ladygin-Vladimir-V" }, { "family_name": "Kim", "given_name": "Dennis S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Bernal-Choban", "given_name": "Camille M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-M" }, { "family_name": "Lohaus", "given_name": "Stefan H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-H" }, { "family_name": "Granroth", "given_name": "Garrett E.", "orcid": "0000-0002-7583-8778", "clpid": "Granroth-Garrett-E" }, { "family_name": "Abernathy", "given_name": "Douglas L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Atomic vibrational dynamics in cuprite Cu_(2)O was studied by inelastic neutron scattering and molecular-dynamics (MD) simulations from 10 K to 900 K. At 300 K, a diffuse inelastic intensity (DII) appeared in the phonon dispersions, and dominated the spectral intensity at higher temperatures. Classical MD simulations with a machine-learning interatomic potential reproduced general features of the DII. Better agreement with experiment was obtained with the addition of a stiffer potential at close approaches of the Cu and O-atoms. The DII originates from random phase shifts of vibrating O atoms that have brief (∼10 fs) anharmonic interactions with neighboring Cu atoms. The spectrum of DII gives information about the interaction time of anharmonic interactions between atoms, and its intensity gives a strength of coupling between vibrating atoms and a thermal bath.
", "doi": "10.1103/physrevmaterials.9.024602", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2025-02-13", "series_number": "2", "volume": "9", "issue": "2", "pages": "024602" }, { "id": "authors:rbrxt-9cf15", "collection": "authors", "collection_id": "rbrxt-9cf15", "cite_using_url": "https://authors.library.caltech.edu/records/rbrxt-9cf15", "type": "article", "title": "Phonon second harmonic generation in NaBr studied by inelastic neutron scattering and computer simulation", "author": [ { "family_name": "Ladygin", "given_name": "V. V.", "orcid": "0000-0002-5697-6956", "clpid": "Ladygin-Vladimir" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-M" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X" }, { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phenomenon of second harmonic generation (SHG) was found for phonons in anharmonic NaBr by inelastic neutron scattering. The temperature dependence of this phonon SHG was measured from 300 K to 650 K. At 300 K the second harmonic (SH) is seen as a high-energy branch around 33 meV, nearly independent of Q. The temperature effective potential (TDEP) method and classical molecular dynamics (MD) simulation with machine learning interatomic potential were able to reproduce the SH, and showed that SHG occurs with the flat transverse optical (TO) phonon branch. A classical model of a nonlinear medium explains the intensity and lifetime of the SH, compared to those of the TO modes. Also successful was a quantum model based on the Heisenberg-Langevin equation for interacting phonons coupled to a thermal bath, which also predicts a spectral distribution of the SH. The measured temperature dependence of the intensity of the second harmonic showed that it follows the Planck distribution of a one-phonon quasiparticle, and not two TO phonons.
", "doi": "10.1103/physrevmaterials.9.015002", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2025-01-24", "series_number": "1", "volume": "9", "issue": "1", "pages": "015002" }, { "id": "authors:99hqa-f7k65", "collection": "authors", "collection_id": "99hqa-f7k65", "cite_using_url": "https://authors.library.caltech.edu/records/99hqa-f7k65", "type": "article", "title": "Kr Adsorption in Porous Carbons: Temperature-Dependent Experimental and Computational Studies", "author": [ { "family_name": "Wang", "given_name": "Ziyi", "orcid": "0000-0003-0811-921X", "clpid": "Wang-Ziyi" }, { "family_name": "Quine", "given_name": "Cullen M.", "orcid": "0000-0002-7301-0969", "clpid": "Quine-Cullen-Mackenzie" }, { "family_name": "Saunders", "given_name": "Claire N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-Nicole" }, { "family_name": "Bernal-Choban", "given_name": "Camille M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-Marie" }, { "family_name": "Ahn", "given_name": "Channing C.", "orcid": "0000-0003-3038-6509", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The temperature dependence of the adsorption energy of krypton adsorption on activated carbon materials was studied by experiment and simulation. Adsorption isotherms were measured at temperatures from 250 to 330 K and analyzed with Henry's law. The adsorption energy determined from these measurements was found to weaken by more than 10% in this range. Slit pore widths for simulations in this work were modeled by the removal of integral numbers of planes in graphite. Vibrational dynamics of the krypton adsorbate and the carbon atom adsorbent were calculated with the stochastic temperature-dependent effective potential (sTDEP) method, using energetics from density functional theory (DFT) with the many-body dispersion energy method (MBD). Thermal displacements of carbon atoms had a negligible effect on the adsorption energy. The width of the slit pore had the greatest effect on the surface dynamics and the energies of the adsorbate atoms at different temperatures. Assuming a distribution of pore widths, the Boltzmann distribution of site occupancies causes a large weakening of the thermally averaged adsorption energy at higher temperatures.", "doi": "10.1021/acs.langmuir.4c02194", "issn": "0743-7463", "publisher": "American Chemical Society", "publication": "Langmuir", "publication_date": "2024-12-10", "series_number": "49", "volume": "40", "issue": "49", "pages": "25793\u201325799" }, { "id": "authors:7x7bt-e0415", "collection": "authors", "collection_id": "7x7bt-e0415", "cite_using_url": "https://authors.library.caltech.edu/records/7x7bt-e0415", "type": "article", "title": "Pressure induced Invar effect in Fe\u2085\u2085\u2062Ni\u2084\u2085: An experimental study with nuclear resonant scattering", "author": [ { "family_name": "Guzman", "given_name": "P.", "orcid": "0000-0002-9726-8315", "clpid": "Guzman-Pedro" }, { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-Haegeli" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-C-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Zhao", "given_name": "J. Y." }, { "family_name": "Shen", "given_name": "G." }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169" }, { "family_name": "Alp", "given_name": "E. E." }, { "family_name": "Lavina", "given_name": "B.", "orcid": "0000-0002-8556-7916" } ], "abstract": "Pressure-dependent synchrotron x-ray diffraction (XRD), nuclear resonant inelastic x-ray scattering (NRIXS), and nuclear forward scattering (NFS) measurements were made on \u2075\u2077Fe\u2085\u2085Ni\u2084\u2085. XRD measurements were at 298 and 392 K at pressures up to 20 GPa, confirming a pressure-induced Invar effect between 7 and 13 GPa. A decrease of the \u2075\u2077Fe magnetic moment was found in NFS measurements under pressure, showing an increase in magnetic entropy. The 57Fe phonon density of states (DOS) was obtained from NRIXS measurements. The low thermal expansion in the high-pressure Invar region originates from a competition between the thermal expansion from spins and phonons as calculated from Maxwell relations. The longitudinal phonon modes changed their pressure dependence near the Curie transition, which is evidence for a spin-phonon interaction.
", "doi": "10.1103/physrevb.110.144419", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2024-10-11", "series_number": "14", "volume": "110", "issue": "14", "pages": "144419" }, { "id": "authors:x2tkg-hze31", "collection": "authors", "collection_id": "x2tkg-hze31", "cite_using_url": "https://authors.library.caltech.edu/records/x2tkg-hze31", "type": "article", "title": "A miniaturized piezoelectric M\u00f6ssbauer spectrometer with feedback control", "author": [ { "family_name": "Guzman", "given_name": "P.", "orcid": "0000-0002-9726-8315", "clpid": "Guzman-Pedro" }, { "family_name": "Quine", "given_name": "C. M.", "orcid": "0000-0002-7301-0969", "clpid": "Quine-Cullen-M" }, { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-H" }, { "family_name": "Schul", "given_name": "L.", "orcid": "0009-0007-1948-936X", "clpid": "Schul-Louise" }, { "family_name": "Toda", "given_name": "R.", "orcid": "0000-0003-1940-3347" }, { "family_name": "Scott", "given_name": "V. J.", "orcid": "0000-0002-0267-9833", "clpid": "Scott-Valerie-J" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A M\u00f6ssbauer spectrometer was built and evaluated using an amplified piezoelectric actuator under feedback control for the Doppler velocity drive. The actuator was driven with a quadratic displacement waveform, giving a linear velocity profile. The optimization of the piezoelectric Doppler drive under feedback control was performed with measurements from a laser Doppler vibrometer. \u2075\u2077Fe M\u00f6ssbauer spectra of \u03b1-iron in transmission geometry show minimal peak distortions. The performance of this piezoelectric Doppler drive makes M\u00f6ssbauer spectrometry possible in applications requiring small size, mass, and low cost.
", "doi": "10.1063/5.0157651", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "2023-11", "series_number": "11", "volume": "94", "issue": "11", "pages": "115107" }, { "id": "authors:w1qnw-p1p21", "collection": "authors", "collection_id": "w1qnw-p1p21", "cite_using_url": "https://authors.library.caltech.edu/records/w1qnw-p1p21", "type": "article", "title": "A thermodynamic explanation of the Invar effect", "author": [ { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-Haegeli" }, { "family_name": "Heine", "given_name": "M.", "orcid": "0000-0002-4882-6712", "clpid": "Heine-Matthew" }, { "family_name": "Guzman", "given_name": "P.", "orcid": "0000-0002-9726-8315", "clpid": "Guzman-Pedro-G" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-M" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Shen", "given_name": "G.", "orcid": "0000-0001-5146-1147", "clpid": "Shen-Guoyin" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Broido", "given_name": "D.", "orcid": "0000-0003-0182-4450", "clpid": "Broido-David" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The anomalously low thermal expansion of Fe\u2013Ni Invar has long been associated with magnetism, but to date, the microscopic underpinnings of the Invar behaviour have eluded both theory and experiment. Here we present nuclear resonant X-ray scattering measurements of the phonon and magnetic entropies under pressure. By applying a thermodynamic Maxwell relation to these data, we obtain the separate phonon and magnetic contributions to thermal expansion. We find that the Invar behaviour stems from a competition between phonons and spins. In particular, the phonon contribution to thermal expansion cancels the magnetic contribution over the 0\u20133\u2009GPa pressure range of Invar behaviour. At pressures above 3\u2009GPa, the cancellation is lost, but our analysis reproduces the positive thermal expansion measured separately by synchrotron X-ray diffractometry. Ab initio calculations informed by experimental data show that spin\u2013phonon interactions improve the accuracy of this cancellation over the range of Invar behaviour. Spin\u2013phonon interactions also explain how different phonon modes have different energy shifts with pressure.
", "doi": "10.1038/s41567-023-02142-z", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2023-07-27" }, { "id": "authors:fhg6z-rr491", "collection": "authors", "collection_id": "fhg6z-rr491", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230328-706770500.46", "type": "article", "title": "Vibrational dynamics in the undercooled liquid of ultra-fragile metallic glasses", "author": [ { "family_name": "Smith", "given_name": "Hillary L.", "orcid": "0000-0001-6155-7812", "clpid": "Smith-Hillary-L" }, { "family_name": "Saunders", "given_name": "Claire N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Bernal-Choban", "given_name": "Camille", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille" }, { "family_name": "Lohaus", "given_name": "Stefan H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-H" }, { "family_name": "Stoddard", "given_name": "Colby J.", "clpid": "Stoddard-Colby-J" }, { "family_name": "Decker", "given_name": "Lucy K.", "orcid": "0000-0002-5210-6486", "clpid": "Decker-Lucy-K" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Niedziela", "given_name": "Jennifer L.", "clpid": "Niedziela-Jennifer-L" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Na", "given_name": "Jong-Hyun", "clpid": "Na-Jong-Hyun" }, { "family_name": "Demetriou", "given_name": "Marios D.", "clpid": "Demetriou-Marios-D" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The lattice vibrational dynamics in ultra-fragile Pt\u2085\u2087Cu\u2082\u2083P\u2082\u2080 and Pt\u2086\u2080Cu\u2082\u2080P\u2082\u2080 glasses were investigated using in situ inelastic neutron scattering to measure the evolution of the phonon density of states (DOS) through the glass transition, into the undercooled liquid phase, and through crystallization. The phonon DOS curves are remarkably similar for the undercooled liquids and the amorphous solids. The vibrational entropy was obtained with these phonon DOS curves, and changes in vibrational entropy caused by the glass transition are less than 0.05 k_B/atom. For these highly fragile metal/metalloid glasses, the excess vibrational entropy of the undercooled liquid is about 0.5\u20131.5 J mol\u207b\u00b9 K\u207b\u00b9, compared to 0.1 J mol\u207b\u00b9 K\u207b\u00b9 reported earlier for stronger Cu\u2013Zr glasses. Our work suggests that, consistent with our previous report for less fragile metallic glasses, the fraction of the total excess entropy that is vibrational is small, and the discontinuity in excess entropy at the glass transition is mainly due to configurational entropy.", "doi": "10.1016/j.mtla.2023.101710", "issn": "2589-1529", "publisher": "Elsevier", "publication": "Materialia", "publication_date": "2023-03", "volume": "27", "pages": "Art. No. 101710" }, { "id": "authors:daqkd-e3z05", "collection": "authors", "collection_id": "daqkd-e3z05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230328-705664700.13", "type": "article", "title": "Nonharmonic contributions to the high-temperature phonon thermodynamics of Cr", "author": [ { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-M" }, { "family_name": "Smith", "given_name": "H. L.", "orcid": "0000-0001-6155-7812", "clpid": "Smith-Hillary-L" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-Lisa" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Phonon densities of states (DOSs) of body-centered cubic chromium were measured by time-of-flight inelastic neutron scattering at temperatures up to 1493 K. Density functional theory calculations with both quasiharmonic (QH) and anharmonic (AH) methods were performed at temperatures above the N\u00e9el temperature. Features in the phonon DOSs decrease in energy (soften) substantially with temperature. A Born\u2013von K\u00e1rm\u00e1n analysis using fits to the experimental DOSs reveals a softening of almost 17% of the high-transverse phonon branch between 330 and 1493 K. The low-transverse branch changes by approximately half this amount. The AH calculations capture the observed behavior of the two transverse phonon branches, but the QH calculations give some inverted trends. Vibrational entropies from phonons and electrons are obtained, and their sum is in excellent agreement with the entropy of chromium obtained by calorimetry, indicating that above 330 K, no explicit temperature-dependent magnetic contributions are necessary.", "doi": "10.1103/physrevb.107.054312", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2023-02-01", "series_number": "5", "volume": "107", "issue": "5", "pages": "Art. No. 054312" }, { "id": "authors:6e9m7-xbw31", "collection": "authors", "collection_id": "6e9m7-xbw31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220131-281001800", "type": "article", "title": "The temperature dependence of nuclear resonant X-Ray spectra of magnetic iron and cementite", "author": [ { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-H" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "From low temperatures through the Curie temperatures, the phonon density of states (DOS) was measured for bcc \u2075\u2077Fe, and the partial phonon DOS was measured for cementite, \u2075\u2077Fe\u2083C, by nuclear resonant inelastic x-ray scattering (NRIXS). Nuclear forward scattering (NFS) was used to determine the state of magnetization of \u2075\u2077Fe\u2083C. The changes in phonon DOS with magnetization were assessed, and a linear relationship was found between the temperature dependences of the magnetization and the non-quasiharmonic shifts of phonon frequencies. Following the quasiharmonic approximation (QHA) for non-harmonic phonons, a magnetic quasiharmonic theory is developed to account for how phonon frequencies are altered by changes in magnetization. The formalism explains well the discrepancy between the free energy measurements and predictions of the QHA for both bcc iron and cementite. The physical origin of the magnetic Gr\u00fcneisen parameters remains a challenge.", "doi": "10.1007/s10751-021-01750-6", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "2022-12", "series_number": "1", "volume": "243", "issue": "1", "pages": "Art. No. 5" }, { "id": "authors:geav8-x0g29", "collection": "authors", "collection_id": "geav8-x0g29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221010-454096500.21", "type": "article", "title": "Hydrogen Adsorption and Isotope Mixing on Copper-Functionalized Activated Carbons", "author": [ { "family_name": "Quine", "given_name": "Cullen M.", "orcid": "0000-0002-7301-0969", "clpid": "Quine-Cullen-M" }, { "family_name": "Smith", "given_name": "Hillary L.", "orcid": "0000-0001-6155-7812", "clpid": "Smith-Hillary-L" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-Channing-C" }, { "family_name": "Hasse-Zamudio", "given_name": "Ariel", "clpid": "Hasse-Zamudio-Ariel" }, { "family_name": "Boyd", "given_name": "David A.", "clpid": "Boyd-David-A" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "High-specific surface area (SSA) carbons were functionalized with copper nanoclusters and evaluated as potential hydrogen storage materials. The adsorption and desorption behaviors of the copper-functionalized material and pristine high-SSA carbon are compared between 77 and 400 K using adsorption isotherms up to 10 MPa and by temperature-programmed desorption of isotopic hydrogen. The high-SSA activated carbon with copper nanoclusters exhibited two desorption behaviors. (1) A desorption peak at 120 K, which was associated with physisorption on carbon, and (2) a desorption peak at 310 K, which was associated with a chemisorption process involving copper. The desorption from copper was strongly dependent on the hydrogen pressure used for loading, and dissociation of the hydrogen could be avoided by loading at low temperature and pressure. An enhancement of hydrogen uptake in the low-coverage (Henry's law) regime at ambient temperatures with copper nanoclusters was observed, demonstrating an increased adsorption enthalpy with the copper-modified material. Binding site energies of 6 and 20 kJ/mol for H2 physisorption and H chemisorption, respectively, were obtained from fits to isotherms.", "doi": "10.1021/acs.jpcc.2c02960", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2022-10-06", "series_number": "39", "volume": "126", "issue": "39", "pages": "16579-16586" }, { "id": "authors:wxbb5-nzk02", "collection": "authors", "collection_id": "wxbb5-nzk02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220601-675495000", "type": "article", "title": "Thermal expansion and phonon anharmonicity of cuprite studied by inelastic neutron scattering and ab initio calculations", "author": [ { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Smith", "given_name": "H. L.", "orcid": "0000-0001-6155-7812", "clpid": "Smith-Hillary-L" }, { "family_name": "Weadock", "given_name": "N. J.", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-Nicholas-J" }, { "family_name": "Omelchenko", "given_name": "S. T.", "orcid": "0000-0003-1104-9291", "clpid": "Omelchenko-Stefan-T" }, { "family_name": "Granroth", "given_name": "G. E.", "orcid": "0000-0002-7583-8778", "clpid": "Granroth-Garrett-E" }, { "family_name": "Bernal-Choban", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Choban-Camille-M" }, { "family_name": "Lohaus", "given_name": "S. H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-Stefan-H" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering measurements were performed with a time-of-flight chopper spectrometer to observe phonons in all parts of the Brillouin zone of a single crystal of cuprite Cu\u2082O. We reduced the experimental data to phonon dispersions in the high-symmetry directions, and changes between 10 and 300 K are reported. In this paper, we show ab initio quasiharmonic (QH) and anharmonic (AH) calculations of phonon dispersions. We performed all AH calculations with a temperature-dependent effective potential method. Both QH and AH calculations account for the small negative thermal expansion of cuprite at low temperatures. However, the measured temperature-dependent phonon behavior was predicted more accurately with the AH calculations than the QH ones. Nevertheless, at 300 K, the cubic AH used in this paper did not entirely account for the experimental phonon dispersions in cuprite.", "doi": "10.1103/physrevb.105.174308", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2022-05-01", "series_number": "17", "volume": "105", "issue": "17", "pages": "Art. No. 174308" }, { "id": "authors:wecre-mjf63", "collection": "authors", "collection_id": "wecre-mjf63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211202-191328092", "type": "article", "title": "Magmatic and post-magmatic evolution of post-collisional rare-metal bearing granite: The Neoproterozoic Homrit Akarem Granitic Intrusion, south Eastern Desert of Egypt, Arabian-Nubian Shield", "author": [ { "family_name": "Abuamarah", "given_name": "Bassam A.", "orcid": "0000-0001-8272-0367", "clpid": "Abuamarah-Bassam-A" }, { "family_name": "Azer", "given_name": "Mokhles K.", "orcid": "0000-0002-3711-8630", "clpid": "Azer-Mokhles-K" }, { "family_name": "Seddik", "given_name": "Amany M. A.", "clpid": "Seddik-Amany-M-A" }, { "family_name": "Asimow", "given_name": "Paul D.", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Guzman", "given_name": "Pedro", "clpid": "Guzman-Pedro" }, { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Wilner", "given_name": "M. J.", "clpid": "Wilner-M-J" }, { "family_name": "Dalleska", "given_name": "Nathan", "orcid": "0000-0002-2059-1587", "clpid": "Dalleska-Nathan-F" }, { "family_name": "Darwish", "given_name": "Mahmoud H.", "orcid": "0000-0002-8930-6422", "clpid": "Darwish-Mahmoud-H" } ], "abstract": "The Homrit Akarem granitic intrusion (HAGI) outcrops near the western edge of the south Eastern Desert basement exposure in Egypt. It is a composite of two cogenetic intrusive bodies: an early albite granite phase shallowly emplaced at the apex of a magmatic cupola, and a later subjacent pink granite phase with a marginal zone of muscovite granite and better preservation of magmatic features. Mineral chemistry of primary biotite and garnet, together with whole-rock chemistry, identify the HAGI as a highly fractionated A-type peraluminous intrusion. The chemistry of F-dominant, Li-bearing, Fe\u00b3\u207a-rich primary magmatic mica in the pink granite resembles that typically found in highly evolved Nb-Y-F pegmatites. The HAGI is the evolved product of a primary magma generated by partial melting of juvenile crust of the Arabian-Nubian Shield (ANS), emplaced along a regional strike-slip fault system that promoted its ascent. The main emplacement mechanism and evolutionary sequence of the HAGI was magmatic, although secondary minerals and textures resulting from hydrothermal fluid interactions are observed, especially at its margins. Primary columbite-(Mn) crystallized from melt and was partly replaced by secondary fluorcalciomicrolite. The high fluorine content of magmatic fluids exsolved from the intrusion is indicated by quartz-fluorite veins, greisenization, albitization, and F-bearing secondary oxide minerals. The magmatic derivation of this fluid is demonstrated by the F-dominant primary mica, a siderophyllite-polylithionite solid solution commonly known as zinnwaldite. The chemistry of zinnwaldite constrains the F/OH activity ratio and oxygen fugacity of its parental melt and thereby resolves the ambiguity between pressure and the effects of F in controlling the normative quartz content of rare-metal granites. The HAGI is less mineralized than the post-collisional rare-metal granites found further east in the south Eastern Desert, replicating a trend observed previously in the central Eastern Desert and suggesting that east-west zoning in rare metal enrichment is a persistent feature across latitudes at the western edge of the ANS.", "doi": "10.1016/j.chemer.2021.125840", "issn": "0009-2819", "publisher": "Elsevier", "publication": "Chemie der Erde - Geochemistry", "publication_date": "2022-04", "series_number": "1", "volume": "82", "issue": "1", "pages": "Art. No. 125840" }, { "id": "authors:q6seq-adz91", "collection": "authors", "collection_id": "q6seq-adz91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210421-095643731", "type": "article", "title": "Prediction and observation of intermodulation sidebands from anharmonic phonons in NaBr", "author": [ { "family_name": "Shen", "given_name": "Y.", "clpid": "Shen-Y" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-Claire-N" }, { "family_name": "Bernal", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-Camille-M" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Williams", "given_name": "T. J.", "clpid": "Williams-T-J" }, { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-Michael-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A quantum Langevin model, like models from optomechanics, was developed for phonons. It predicts intermodulation phonon sidebands (IPSs) in anharmonic crystals. Ab initio calculations of anharmonic phonons in rock-salt NaBr showed these spectral features as many-body effects. Modern inelastic neutron scattering measurements on a crystal of NaBr at 300 K revealed diffuse intensity at high phonon energy from a predicted upper IPS. The transverse optical (TO) part of the new features originates from phonon intermodulation between the transverse acoustic (TA) and TO phonons. The longitudinal optical spectral features originate from three-phonon coupling between the TA modes and the TO lattice modes. The partner lower IPS proves to be an intrinsic localized mode. Interactions with the thermal bath broaden and redistribute the spectral weight of the IPS pair. These sidebands are a probe of the anharmonicity and quantum noise of phonons in NaBr and suggest novel interactions between photons and phonons.", "doi": "10.1103/physrevb.103.134302", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2021-04-01", "series_number": "13", "volume": "103", "issue": "13", "pages": "Art. No. 134302" }, { "id": "authors:82afh-mep05", "collection": "authors", "collection_id": "82afh-mep05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210128-095301970", "type": "article", "title": "Interface pinning causes the hysteresis of the hydride transformation in binary metal hydrides", "author": [ { "family_name": "Weadock", "given_name": "Nicholas J.", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-Nicholas-J" }, { "family_name": "Voorhees", "given_name": "Peter W.", "orcid": "0000-0003-2769-392X", "clpid": "Voorhees-Peter-W" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Hydriding and dehydriding transitions in bulk and nanocrystalline binary metal hydrides were studied using the Pd-H model system by measuring pressure-composition isotherms with in situ x-ray diffractometry. Nanocrystalline Pd showed a smaller pressure hysteresis, solvus hysteresis, and hysteresis in lattice parameter, compared to bulk Pd. The time-dependence of pressure equilibration was measured after dosing with aliquots of hydrogen, giving equilibration times that were much faster in the single-phase regions than in the two-phase plateaus. In the broad two-phase plateaus, the pressure relaxations were exponential functions of time. An explanation of hysteresis is developed that is based on a dissipative potential barrier that impedes the motion of the interface due to interactions between lattice defects and the two-phase interface. The exponential pressure relaxations and hysteresis are consistent for this mechanism. For a simple model of the pinning potential, the potential barrier maximum is an order of magnitude less than typical grain boundary energies. These pinning effects are substantially different in the nanocrystalline Pd, suggesting differences in the hydriding mechanism.", "doi": "10.1103/PhysRevMaterials.5.013604", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2021-01", "series_number": "1", "volume": "5", "issue": "1", "pages": "Art. No. 013604" }, { "id": "authors:ddkr1-rvh11", "collection": "authors", "collection_id": "ddkr1-rvh11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201117-105350111", "type": "article", "title": "Temperature-dependent phonon lifetimes and thermal conductivity of silicon by inelastic neutron scattering and ab initio calculations", "author": [ { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Shulumba", "given_name": "N.", "orcid": "0000-0002-2374-7487", "clpid": "Shulumba-N" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-C-N" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Herriman", "given_name": "J. E.", "orcid": "0000-0003-4769-1403", "clpid": "Herriman-J-E" }, { "family_name": "Niedziela", "given_name": "J. L.", "orcid": "0000-0002-2990-923X", "clpid": "Niedziela-J-L" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Li", "given_name": "C. W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering on a single crystal of silicon was performed at temperatures from 100 to 1500 K. These experimental data were reduced to obtain phonon spectral intensity at all wave vectors \u2192Q and frequencies \u03c9 in the first Brillouin zone. Thermal broadenings of the phonon peaks were obtained by fitting and by calculating with an iterative ab initio method that uses thermal atom displacements on an ensemble of superlattices. Agreement between the calculated and experimental broadenings was good, with possible discrepancies at the highest temperatures. Distributions of phonon widths versus phonon energy had similar shapes for computation and experiment. These distributions grew with temperature but maintained similar shapes. Parameters from the ab initio calculations were used to obtain the thermal conductivity from the Boltzmann transport equation, which was in good agreement with experimental data. Despite the high group velocities of longitudinal acoustic phonons, their shorter lifetimes reduced their contribution to the thermal conductivity, which was dominated by transverse acoustic modes.", "doi": "10.1103/physrevb.102.174311", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2020-11-01", "series_number": "17", "volume": "102", "issue": "17", "pages": "Art. No. 174311" }, { "id": "authors:0hb0g-7t468", "collection": "authors", "collection_id": "0hb0g-7t468", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191111-085942260", "type": "article", "title": "Anharmonic Origin of the Giant Thermal Expansion of NaBr", "author": [ { "family_name": "Shen", "given_name": "Y.", "orcid": "0000-0001-6838-0925", "clpid": "Shen-Yang" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-C-N" }, { "family_name": "Bernal", "given_name": "C. M.", "orcid": "0000-0001-7550-3153", "clpid": "Bernal-C-M" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-M-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "All phonons in a single crystal of NaBr are measured by inelastic neutron scattering at temperatures of 10, 300, and 700 K. Even at 300 K, the phonons, especially the longitudinal-optical phonons, show large shifts in frequencies and show large broadenings in energy owing to anharmonicity. Ab initio computations are first performed with the quasiharmonic approximation (QHA) in which the phonon frequencies depend only on \nV and on T only insofar as it alters V by thermal expansion. This QHA is an unqualified failure for predicting the temperature dependence of phonon frequencies, even 300 K, and the thermal expansion is in error by a factor of 4. Ab initio computations that include both anharmonicity and quasiharmonicity successfully predict both the temperature dependence of phonons and the large thermal expansion of NaBr. The frequencies of longitudinal-optical phonon modes decrease significantly with temperature owing to the real part of the phonon self-energy from explicit anharmonicity originating from the cubic anharmonicity of nearest-neighbor NaBr bonds. Anharmonicity is not a correction to the QHA predictions of thermal expansion and thermal phonon shifts but dominates the behavior.", "doi": "10.1103/PhysRevLett.125.085504", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2020-08-21", "series_number": "8", "volume": "125", "issue": "8", "pages": "Art. No. 085504" }, { "id": "authors:sm32b-ea753", "collection": "authors", "collection_id": "sm32b-ea753", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200811-114716456", "type": "article", "title": "Thermodynamic stability and contributions to the Gibbs free energy of nanocrystalline Ni\u2083Fe", "author": [ { "family_name": "Lohaus", "given_name": "Stefan H.", "orcid": "0000-0002-4430-3834", "clpid": "Lohaus-S-H" }, { "family_name": "Johnson", "given_name": "Michel B.", "clpid": "Johnson-Michel-B" }, { "family_name": "Ahnn", "given_name": "Peter F.", "clpid": "Ahnn-P-F" }, { "family_name": "Saunders", "given_name": "Claire N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-C-N" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "White", "given_name": "Mary Anne", "orcid": "0000-0001-8142-0004", "clpid": "White-Mary-Anne" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The heat capacities of nanocrystalline Ni\u2083Fe and control materials with larger crystallites were measured from \n0.4\u2013300 K. The heat capacities were integrated to obtain the enthalpy, entropy, and Gibbs free energy and to quantify how these thermodynamic functions are altered by nanocrystallinity. From the phonon density of states (DOS) measured by inelastic neutron scattering, we find that the Gibbs free energy is dominated by phonons and that the larger heat capacity of the nanomaterial below 100 K is attributable to its enhanced phonon DOS at low energies. Besides electronic and magnetic contributions, the nanocrystalline material has an additional contribution at higher temperatures, consistent with phonon anharmonicity. The nanocrystalline material shows a stronger increase with temperature of both the enthalpy and entropy compared to the bulk sample. Its entropy exceeds that of the bulk material by 0.4 k_B/atom at 300 K. This is insufficient to overcome the enthalpy of grain boundaries and defects in the nanocrystalline material, making it thermodynamically unstable with respect to the bulk control material.", "doi": "10.1103/physrevmaterials.4.086002", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2020-08", "series_number": "8", "volume": "4", "issue": "8", "pages": "Art. No. 086002" }, { "id": "authors:k8fd0-7p714", "collection": "authors", "collection_id": "k8fd0-7p714", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200611-131726422", "type": "article", "title": "Phonon thermodynamics and elastic behavior of GaAs at high temperatures and pressures", "author": [ { "family_name": "Herriman", "given_name": "Jane E.", "orcid": "0000-0003-4769-1403", "clpid": "Herriman-J-E" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phonons of wurtzite and zinc blende GaAs were calculated at simultaneously elevated temperature and pressure, and elastic constants were calculated as functions of pressure. Pressure caused instabilities of shorter-wavelength transverse acoustic modes in both wurtzite and zinc blende GaAs, causing them to fall to zero at 18 and 20 GPa, respectively. The Born stability criteria, which depend on elastic constants and only long wavelength phonons, therefore overestimated the pressure needed to induce instability at 0 K. At elevated temperatures, explicit anharmonicity pushes the onset of instability to higher pressures in both wurtzite and zinc blende GaAs. Phonon linewidth and densities of states data showed that the quasiharmonic approximation failed to account for temperature-induced phonon frequency shifts, and the quasiharmonic approximation became less reliable at elevated pressure. In general, the number of three-phonon processes increased with pressure, thereby increasing the temperature-driven broadening of phonon spectral lineshapes.", "doi": "10.1103/physrevb.101.214108", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2020-06-01", "series_number": "21", "volume": "101", "issue": "21", "pages": "Art. No. 214108" }, { "id": "authors:v089k-m1d78", "collection": "authors", "collection_id": "v089k-m1d78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200313-142323674", "type": "article", "title": "Temperature dependence of electron-phonon interactions in vanadium", "author": [ { "family_name": "Yang", "given_name": "F. C.", "orcid": "0000-0002-5615-5170", "clpid": "Yang-Fred-Chae-Reem" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "First-principles calculations were used to study the Fermi surface of body-centered cubic vanadium at elevated temperatures. Supercell calculations accounted for effects of thermal atom displacements on band energies, and band unfolding was used to project the spectral weight of the electron states into the Brillouin zone of a standard bcc unit cell. An electronic topological transition (ETT, or Lifshitz transition) occurred near the \u0393 point with increasing temperature, but the large thermal smearings from the atomic disorder and the Fermi-Dirac distribution reduced the effect of this ETT on the electron-phonon interactions. The phonon dispersions showed thermal stiffening of their Kohn anomalies near the \u0393 point and of the longitudinal N phonon mode. In general the effects of the ETT were overcome by the thermal smearing of the Fermi surface that reduces the spanning vector densities for anomalous phonon modes.", "doi": "10.1103/physrevb.101.094305", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2020-03-01", "series_number": "9", "volume": "101", "issue": "9", "pages": "Art. No. 094305" }, { "id": "authors:9rtwk-70x95", "collection": "authors", "collection_id": "9rtwk-70x95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191101-153724236", "type": "article", "title": "Entropic elasticity and negative thermal expansion in a simple cubic crystal", "author": [ { "family_name": "Wendt", "given_name": "David", "clpid": "Wendt-David" }, { "family_name": "Bozin", "given_name": "Emil", "clpid": "Bozin-Emil" }, { "family_name": "Neuefeind", "given_name": "Joerg", "clpid": "Neuefeind-Joerg" }, { "family_name": "Page", "given_name": "Katharine", "orcid": "0000-0002-9071-3383", "clpid": "Page-Katharine" }, { "family_name": "Ku", "given_name": "Wei", "clpid": "Ku-Wei" }, { "family_name": "Wang", "given_name": "Limin", "clpid": "Wang-Limin" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Tkachenko", "given_name": "Alexei V.", "clpid": "Tkachenko-Alexei-V" }, { "family_name": "Zaliznyak", "given_name": "Igor A.", "clpid": "Zaliznyak-Igor-A" } ], "abstract": "While most solids expand when heated, some materials show the opposite behavior: negative thermal expansion (NTE). In polymers and biomolecules, NTE originates from the entropic elasticity of an ideal, freely jointed chain. The origin of NTE in solids has been widely believed to be different. Our neutron scattering study of a simple cubic NTE material, ScF\u2083, overturns this consensus. We observe that the correlation in the positions of the neighboring fluorine atoms rapidly fades on warming, indicating an uncorrelated thermal motion constrained by the rigid Sc-F bonds. This leads us to a quantitative theory of NTE in terms of entropic elasticity of a floppy network crystal, which is in remarkable agreement with experimental results. We thus reveal the formidable universality of the NTE phenomenon in soft and hard matter.", "doi": "10.1126/sciadv.aay2748", "pmcid": "PMC6824856", "issn": "2375-2548", "publisher": "American Association for the Advancement of Science", "publication": "Science Advances", "publication_date": "2019-11-01", "series_number": "11", "volume": "5", "issue": "11", "pages": "Art. No. eaay2748" }, { "id": "authors:6twes-zth52", "collection": "authors", "collection_id": "6twes-zth52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-095738529", "type": "article", "title": "An International Laboratory Comparison Study of Volumetric and Gravimetric Hydrogen Adsorption Measurements", "author": [ { "family_name": "Hurst", "given_name": "Katherine E.", "orcid": "0000-0003-4596-9504", "clpid": "Hurst-K-E" }, { "family_name": "Edwards", "given_name": "Bryce", "clpid": "Edwards-Bryce" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "In order to determine a material's hydrogen storage potential, capacity measurements must be robust, reproducible and accurate. Commonly, research reports focus on the gravimetric capacity, and often times the volumetric capacity is not reported. Determining volumetric capacities is not as straight\u2010forward, especially for amorphous materials. This is the first study to compare measurement reproducibly across laboratories for excess and total volumetric hydrogen sorption capacities based on the packing volume. The use of consistent measurement protocols, common analysis, and figure of merits for reporting data in this study, enable the comparison of the results for two different materials. Importantly, the results show good agreement for excess gravimetric capacities amongst the laboratories. Irreproducibility for excess and total volumetric capacities is attributed to real differences in the measured packing volume of the material.", "doi": "10.1002/cphc.201900166", "issn": "1439-4235", "publisher": "Wiley", "publication": "ChemPhysChem", "publication_date": "2019-08-05", "series_number": "15", "volume": "20", "issue": "15", "pages": "1997-2009" }, { "id": "authors:zv6p5-r9t27", "collection": "authors", "collection_id": "zv6p5-r9t27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190321-112730967", "type": "article", "title": "High-Pressure Hydrogen Adsorption on a Porous Electron-Rich Covalent Organonitridic Framework", "author": [ { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-Maxwell" }, { "family_name": "Weadock", "given_name": "Nicholas J.", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-Nicholas-J" }, { "family_name": "Liu", "given_name": "Yiqun", "clpid": "Liu-Yiqun" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-Channing-C" }, { "family_name": "Baker", "given_name": "Sarah E.", "clpid": "Baker-Sarah-E" }, { "family_name": "Landskron", "given_name": "Kai", "orcid": "0000-0001-6170-4704", "clpid": "Landskron-Kai" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We report that a porous, electron-rich, covalent, organonitridic framework (PECONF-4) exhibits an unusually high hydrogen uptake at 77 K, relative to its specific surface area. Chahine's rule, a widely cited heuristic for hydrogen adsorption, sets a maximum adsorptive uptake of 1 wt % hydrogen at 77 K per 500 m^2 of the adsorbent surface area. High-pressure hydrogen adsorption measurements in a Sieverts apparatus showed that PECONF-4 exceeds Chahine's rule by 50%. The Brunauer\u2013Emmett\u2013Teller (BET) specific surface area of PECONF-4 was measured redundantly with nitrogen, argon, and carbon dioxide and found to be between 569 \u00b1 2 and 676 \u00b1 13 m^2 g^(\u20131). Furthermore, hydrogen on PECONF-4 has a high heat of adsorption, in excess of 9 kJ mol^(\u20131).", "doi": "10.1021/acsomega.8b03206", "pmcid": "PMC6648737", "issn": "2470-1343", "publisher": "American Chemical Society", "publication": "ACS Omega", "publication_date": "2019-01", "series_number": "1", "volume": "4", "issue": "1", "pages": "444-448" }, { "id": "authors:9044q-46f29", "collection": "authors", "collection_id": "9044q-46f29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181206-133340102", "type": "article", "title": "Phonon thermodynamics and elastic behavior of GaN at high temperatures and pressures", "author": [ { "family_name": "Herriman", "given_name": "Jane E.", "clpid": "Herriman-Jane-E" }, { "family_name": "Hellman", "given_name": "Olle", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The effects of temperature and pressure on the phonons of GaN were calculated for both the wurtzite and zinc-blende structures. The quasiharmonic approximation (QHA) gave reasonable results for the temperature dependence of the phonon DOS at zero pressure but unreliably predicted the combined effects of temperature and pressure. Pressure was found to change the explicit anharmonicity, altering the thermal shifts of phonons and more notably qualitatively changing the evolution of phonon lifetimes with increasing temperature. These effects were largest for the optical modes, and phonon frequencies below approximately 5 THz were adequately predicted with the QHA. The elastic anisotropies of GaN in both wurtzite and zinc-blende structures were calculated from the elastic constants as a function of pressure at 0 K. The elastic anisotropy increased with pressure until reaching elastic instabilities at 40 GPa (zinc blende) and 65 GPa (wurtzite). The calculated instabilities are consistent with proposed transformation pathways to rocksalt GaN and place upper bounds on the pressures at which wurtzite and zinc-blende GaN can be metastable.", "doi": "10.1103/PhysRevB.98.214105", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-12-01", "series_number": "21", "volume": "98", "issue": "21", "pages": "Art. No. 214105" }, { "id": "authors:asjfr-5tz53", "collection": "authors", "collection_id": "asjfr-5tz53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181009-094209133", "type": "article", "title": "Temperature dependence of phonons in FeGe_2", "author": [ { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Shen", "given_name": "Yang", "clpid": "Shen-Yang" }, { "family_name": "Kim", "given_name": "Dennis S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Yang", "given_name": "Fred C.", "orcid": "0000-0002-5615-5170", "clpid": "Yang-Fred-Chae-Reem" }, { "family_name": "Adams", "given_name": "C. P.", "clpid": "Adams-C-P" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was used to measure phonon dispersions in a single crystal of FeGe_2 with the C16 structure at 300, 500, and 635 K. Phonon densities of states (DOS) were also measured on polycrystalline FeGe_2 from 325 to 1050 K, and the Fe partial DOS was obtained from polycrystalline ^(57)FeGe_2 at 300 K using nuclear resonant inelastic x-ray scattering. The dominant feature in the temperature dependence of the phonon spectrum is thermal broadening of high-energy modes. The energy shifts of the low- and high-energy parts of the spectrum were almost the same. DFT calculations performed with the quasiharmonic approximation gave results in moderate agreement with the experimental thermal energy shifts, although the isobaric Gr\u00fcneisen parameter calculated from the quasiharmonic model was smaller than that from measurements. The thermal broadening of the phonon spectrum and dispersions, especially at high energies, indicates a cubic anharmonicity to second order that should also induce phonon shifts. We show that different anharmonic contributions cancel out, giving average phonon shifts in moderate agreement to calculations with the quasiharmonic approximation. The different parts of the large phonon contribution to the entropy are separated for FeGe_2, showing modest but interpretable anharmonic contributions.", "doi": "10.1103/PhysRevMaterials.2.103602", "issn": "2475-9953", "publisher": "American Physical Society", "publication": "Physical Review Materials", "publication_date": "2018-10", "series_number": "10", "volume": "2", "issue": "10", "pages": "Art. No. 103602" }, { "id": "authors:6324z-ks791", "collection": "authors", "collection_id": "6324z-ks791", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180703-112951439", "type": "article", "title": "Temperature dependence of phonons in Pd_3Fe through the Curie temperature", "author": [ { "family_name": "Yang", "given_name": "F. C.", "orcid": "0000-0002-5615-5170", "clpid": "Yang-Fred-Chae-Reem" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Saunders", "given_name": "C. N.", "orcid": "0000-0001-7973-3722", "clpid": "Saunders-C-N" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "Paul", "clpid": "Chow-Paul" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Iron phonon partial densities of states of Pd_3^(57)Fe were measured from room temperature through the Curie transition at 500 K using nuclear resonant inelastic x-ray scattering. The experimental results were compared to ab initio spin-polarized calculations that model the finite-temperature thermodynamic properties of L1_2-ordered Pd_3Fe with stochastically generated atomic displacements, coupled with magnetic special quasirandom structures of noncollinear magnetic moments. The scattering measurements and first-principles calculations show that the Fe partial vibrational entropy is close to what is predicted by the quasiharmonic approximation owing to a cancellation of effects. Anharmonicity and a magnon-phonon interaction approximately cancel a ferromagnetic optical phonon stiffening.", "doi": "10.1103/PhysRevB.98.024301", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2018-07-01", "series_number": "2", "volume": "98", "issue": "2", "pages": "Art. No. 024301" }, { "id": "authors:djdne-tf048", "collection": "authors", "collection_id": "djdne-tf048", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171011-123647370", "type": "article", "title": "A Thermodynamic Investigation of Adsorbate-Adsorbate Interactions of Carbon Dioxide on Nanostructured Carbons", "author": [ { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A thermodynamic study of carbon dioxide adsorption on a zeolite-templated carbon (ZTC), a superactivated carbon (MSC-30) and an activated carbon (CNS-201) was carried out at temperatures from 241 to 478 K and pressures up to 5.5\u202210^6 Pa. Excess adsorption isotherms were fitted with generalized Langmuir-type equations, allowing the isosteric heats of adsorption and adsorbed-phase heat capacities to be obtained as a function of absolute adsorption. On MSC-30, a superactivated carbon, the isosteric heat of carbon dioxide adsorption increases with occupancy from 19 to 21 kJ\u2022mol^(\u22121), before decreasing at high loading. This increase is attributed to attractive adsorbate-adsorbate intermolecular interactions as evidenced by the slope and magnitude of the increase in isosteric heat and the adsorbed-phase heat capacities. An analysis of carbon dioxide adsorption on ZTC indicates a high degree of binding-site homogeneity. A generalized Law of Corresponding States analysis indicates lower carbon dioxide adsorption than expected.", "doi": "10.1002/aic.15996", "issn": "0001-1541", "publisher": "Wiley", "publication": "AIChE Journal", "publication_date": "2018-03", "series_number": "3", "volume": "64", "issue": "3", "pages": "1026-1033" }, { "id": "authors:3071g-j0t31", "collection": "authors", "collection_id": "3071g-j0t31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180214-150839490", "type": "article", "title": "Nuclear quantum effect with pure anharmonicity and the anomalous thermal expansion of silicon", "author": [ { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Herriman", "given_name": "J. E.", "clpid": "Herriman-Jane-E" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Shulumba", "given_name": "N.", "orcid": "0000-0002-2374-7487", "clpid": "Shulumba-Nina" }, { "family_name": "Niedziela", "given_name": "J. L.", "orcid": "0000-0002-2990-923X", "clpid": "Niedziela-Jennifer-L" }, { "family_name": "Li", "given_name": "C. W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Despite the widespread use of silicon in modern technology, its peculiar thermal expansion is not well understood. Adapting harmonic phonons to the specific volume at temperature, the quasiharmonic approximation, has become accepted for simulating the thermal expansion, but has given ambiguous interpretations for microscopic mechanisms. To test atomistic mechanisms, we performed inelastic neutron scattering experiments from 100 K to 1,500 K on a single crystal of silicon to measure the changes in phonon frequencies. Our state-of-the-art ab initio calculations, which fully account for phonon anharmonicity and nuclear quantum effects, reproduced the measured shifts of individual phonons with temperature, whereas quasiharmonic shifts were mostly of the wrong sign. Surprisingly, the accepted quasiharmonic model was found to predict the thermal expansion owing to a large cancellation of contributions from individual phonons.", "doi": "10.1073/pnas.1707745115", "pmcid": "PMC5834665", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2018-02-27", "series_number": "9", "volume": "115", "issue": "9", "pages": "1992-1997" }, { "id": "authors:0n2md-ddy70", "collection": "authors", "collection_id": "0n2md-ddy70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171006-131136299", "type": "article", "title": "High capacity V-based metal hydride electrodes for rechargeable batteries", "author": [ { "family_name": "Yang", "given_name": "Heng", "orcid": "0000-0001-7431-932X", "clpid": "Yang-Heng" }, { "family_name": "Weadock", "given_name": "Nicholas J.", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-N-J" }, { "family_name": "Tan", "given_name": "Hongjin", "clpid": "Tan-Hongjin" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We report the successful development of Ti_(29)V_(62\u2212x)Ni_9Cr_x (x = 0, 6, 12) body centered cubic metal hydride (MH) electrodes by addressing vanadium corrosion and dissolution in KOH solutions. By identifying oxygen as the primary source of corrosion and eliminating oxygen with an Ar-purged cell, the Cr-free Ti_(29)V_(62)Ni_9 alloy electrode achieved a maximum capacity of 594 mAh g^(-1), double the capacity of commercial AB_5 MH electrodes. With coin cells designed to minimize oxygen evolution, the cycle stability of a Ti_(29)V_(62)Ni_9 alloy electrode was greatly improved with either vanadate ion additions to the electrolyte or Cr-substitution in the alloy. Together, both approaches resulted in a reversible capacity of around 500 mAh g^(\u22121) for at least 200 cycles. We performed energy density calculations for a 100 W h MH\u2013air cell utilizing the high capacity Ti_(29)V_(62\u2212x)Ni_9Cr_x electrodes and found that these cells are comparable in energy density to state-of-the-art Li-ion batteries.", "doi": "10.1039/c7ta07396h", "issn": "2050-7488", "publisher": "Royal Society of Chemistry", "publication": "Journal of Materials Chemistry A", "publication_date": "2017-11-07", "series_number": "41", "volume": "5", "issue": "41", "pages": "21785-21794" }, { "id": "authors:n85t7-yjr69", "collection": "authors", "collection_id": "n85t7-yjr69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170411-135835964", "type": "article", "title": "Separating the configurational and vibrational entropy contributions in metallic glasses", "author": [ { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Hoff", "given_name": "Andrew", "clpid": "Hoff-A" }, { "family_name": "Garrett", "given_name": "Glenn R.", "clpid": "Garrett-G-R" }, { "family_name": "Kim", "given_name": "Dennis S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Yang", "given_name": "Fred C.", "orcid": "0000-0002-5615-5170", "clpid": "Yang-Fred-Chae-Reem" }, { "family_name": "Lucas", "given_name": "Matthew S.", "clpid": "Lucas-M-S" }, { "family_name": "Swan-Wood", "given_name": "Tabitha", "clpid": "Swan-Wood-T-L" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Demetriou", "given_name": "Marios D.", "clpid": "Demetriou-M-D" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Glassy materials exist in nature and play a critical role in technology, but key differences between the glass, liquid and crystalline phases are not well understood. Over several decades there has been controversy about the specific heat absorbed as a glass transforms to a liquid\u2014does this originate from vibrational entropy or configurational entropy? Here we report direct in situ measurements of the vibrational spectra of strong and fragile metallic glasses in the glass, liquid and crystalline phases. For both types of material, the measured vibrational entropies of the glass and liquid show a tiny excess over the crystal, representing less than 5% of the total excess entropy measured with step calorimetry. These results reveal that the excess entropy of metallic glasses is almost entirely configurational in origin, consistent with the early theories of Gibbs and co-workers describing the glass transition as a purely configurational transition.", "doi": "10.1038/nphys4142", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2017-09", "series_number": "9", "volume": "13", "issue": "9", "pages": "900-905" }, { "id": "authors:s1ygn-q3p98", "collection": "authors", "collection_id": "s1ygn-q3p98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170320-085615235", "type": "article", "title": "Phonons in Si_(24) at simultaneously elevated temperature and pressure", "author": [ { "family_name": "Tong", "given_name": "Xiao", "clpid": "Tong-Xiao" }, { "family_name": "Xu", "given_name": "Xiaolin", "clpid": "Xu-Xiaolin" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Zhang", "given_name": "Haidong", "clpid": "Zhang-Haidong" }, { "family_name": "Strobel", "given_name": "Timothy A.", "orcid": "0000-0003-0338-4380", "clpid": "Strobel-T-A" }, { "family_name": "Kim", "given_name": "Duck Young", "clpid": "Kim-Duck-Young" } ], "abstract": "Raman spectroscopy was used to measure the frequencies of phonons in Si_(24) with an open clathrate structure at temperatures from 80 to 400 K with simultaneous pressures of 0 to 8 GPa. The frequency shifts of the different phonons were substantially different under either temperature or pressure. The quasiharmonic behavior was isolated by varying pressure at low temperatures, and the anharmonic behavior was isolated by varying temperature at low pressures. Phonon modes dominated by bond bending were anomalous, showing stiffening with temperature and softening with pressure. Both the quasiharmonic behavior and the anharmonic behavior changed markedly with simultaneous changes in temperature \u0394T and pressure \u0394P. With \u0394T = 320 K and \u0394P = 8 GPa, some frequency shifts that scaled with the product \u0394T \u0394P were as large as the shifts from \u0394T and \u0394P alone. The thermodynamic entropy of this material likely has a dependence on \u0394T and \u0394P that cannot be obtained by adding effects from quasiharmonicity and phonon-phonon anharmonicity.", "doi": "10.1103/PhysRevB.95.094306", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2017-03-01", "series_number": "9", "volume": "95", "issue": "9", "pages": "Art. No. 094306" }, { "id": "authors:gdn70-vcq49", "collection": "authors", "collection_id": "gdn70-vcq49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170125-154755765", "type": "article", "title": "Phonons and elasticity of cementite through the Curie temperature", "author": [ { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Herriman", "given_name": "J. E.", "clpid": "Herriman-Jane-E" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Li", "given_name": "J.", "clpid": "Li-J" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Phonon partial densities of states (pDOS) of ^(57)Fe_3 C were measured from cryogenic temperatures through the Curie transition at 460 K using nuclear resonant inelastic x-ray scattering. The cementite pDOS reveal that low-energy acoustic phonons shift to higher energies (stiffen) with temperature before the magnetic transition. This unexpected stiffening suggests strongly nonharmonic vibrational behavior that impacts the thermodynamics and elastic properties of cementite. Density functional theory calculations reproduced the anomalous stiffening observed experimentally in cementite by accounting for phonon-phonon interactions at finite temperatures. The calculations show that the low-energy acoustic phonon branches with polarizations along the [010] direction are largely responsible for the anomalous thermal stiffening. The effect was further localized to the motions of the Fe_(II) site within the orthorhombic structure, which participates disproportionately in the anomalous phonon stiffening.", "doi": "10.1103/PhysRevB.95.024308", "issn": "2469-9950", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2017-01-01", "series_number": "2", "volume": "95", "issue": "2", "pages": "Art. No. 024308" }, { "id": "authors:zd3zk-fm820", "collection": "authors", "collection_id": "zd3zk-fm820", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160808-113911118", "type": "article", "title": "Thermally Driven Electronic Topological Transition in FeTi", "author": [ { "family_name": "Yang", "given_name": "F. C.", "orcid": "0000-0002-5615-5170", "clpid": "Yang-Fred-Chae-Reem" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M^\u2212_5 phonon mode in B2-ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. The thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M^\u2212_5 phonon mode and an adiabatic electron-phonon interaction with an unusual temperature dependence.", "doi": "10.1103/PhysRevLett.117.076402", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2016-08-12", "series_number": "7", "volume": "117", "issue": "7", "pages": "Art. No. 076402" }, { "id": "authors:yrh89-2pf70", "collection": "authors", "collection_id": "yrh89-2pf70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160524-080846455", "type": "article", "title": "A Generalized Law of Corresponding States for the Physisorption of Classical Gases with Cooperative Adsorbate-Adsorbate Interactions", "author": [ { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The Law of Corresponding States for classical gases is well established. Recent attempts at developing an analogous Law of Corresponding States for gas physisorption, however, have had limited success, in part due to the omission of relevant adsorption considerations such as the adsorbate volume and cooperative adsorbate-adsorbate interactions. In this work, we modify a prior Law of Corresponding States for gas physisorption to account for adsorbate volume, and test it with experimental data and a generalized theoretical approach. Furthermore, we account for the recently-reported cooperative adsorbate-adsorbate interactions on the surface of zeolite-templated carbon (ZTC) with an Ising-type model, and in doing so, show that the Law of Corresponding States for gas physisorption remains valid even in the presence of atypically enhanced adsorbate-adsorbate interactions.", "doi": "10.1021/acs.jpcc.6b00289", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2016-06-09", "series_number": "22", "volume": "120", "issue": "22", "pages": "11847-11853" }, { "id": "authors:gwtt3-mh980", "collection": "authors", "collection_id": "gwtt3-mh980", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160606-100905733", "type": "article", "title": "Phonon anharmonicity and components of the entropy in palladium and platinum", "author": [ { "family_name": "Shen", "given_name": "Yang", "clpid": "Shen-Yang" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Tang", "given_name": "Xiaoli", "clpid": "Tang-Xiaoli" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements.", "doi": "10.1103/PhysRevB.93.214303", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2016-06-01", "series_number": "21", "volume": "93", "issue": "21", "pages": "Art. No. 214303" }, { "id": "authors:875fa-vmt96", "collection": "authors", "collection_id": "875fa-vmt96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160502-134646874", "type": "article", "title": "Polaron Mobility and Disordering of the Sodium Sublattice in Triphylite-Na_xFePO_4", "author": [ { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-H-J" }, { "family_name": "Herriman", "given_name": "J. E.", "clpid": "Herriman-J-E" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The interplay between sodium ordering and electron mobility in Na_xFePO_4 was investigated using a combination of synchrotron X-ray diffraction and M\u00f6ssbauer spectrometry. Synchrotron X-ray diffraction measurements were carried out for a range of temperatures between 298 and 553 K. Rietveld analysis of the diffraction patterns was used to determine the temperature of sodium redistribution on the lattice. This diffraction analysis also gives new information about the phase stability of the system. M\u00f6ssbauer spectra were collected in the same temperature range. An analysis of the temperature evolution of the spectral shapes was used to identify the onset of fast electron hopping and determine the polaron hopping rate. The temperature evolution of the iron site occupancies from the M\u00f6ssbauer measurements, combined with the synchrotron diffraction results, shows a relationship between the onset of fast electron dynamics and the loss of local order on the sodium sublattice.", "doi": "10.1021/acs.chemmater.6b00226", "issn": "0897-4756", "publisher": "American Chemical Society", "publication": "Chemistry of Materials", "publication_date": "2016-05-10", "series_number": "9", "volume": "28", "issue": "9", "pages": "3051-3059" }, { "id": "authors:eh7b3-ft650", "collection": "authors", "collection_id": "eh7b3-ft650", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151116-111113865", "type": "article", "title": "MCViNE - An object oriented Monte Carlo neutron ray tracing simulation package", "author": [ { "family_name": "Lin", "given_name": "Jiao Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Granroth", "given_name": "Garrett E.", "orcid": "0000-0002-7583-8778", "clpid": "Granroth-G-E" }, { "family_name": "Abernathy", "given_name": "Douglas L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Lumsden", "given_name": "Mark D.", "clpid": "Lumsden-Mark-D" }, { "family_name": "Winn", "given_name": "Barry", "clpid": "Winn-Barry" }, { "family_name": "Aczel", "given_name": "Adam A.", "clpid": "Aczel-Adam-A" }, { "family_name": "Aivazis", "given_name": "Michael", "clpid": "Aivazis-M" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiple scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. With simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.", "doi": "10.1016/j.nima.2015.11.118", "issn": "0168-9002", "publisher": "Elsevier", "publication": "Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment", "publication_date": "2016-02-21", "volume": "810", "pages": "86-99" }, { "id": "authors:zfg93-kr461", "collection": "authors", "collection_id": "zfg93-kr461", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151123-104238733", "type": "article", "title": "Unusual Entropy of Adsorbed Methane on Zeolite-Templated Carbon", "author": [ { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Methane adsorption at high pressures and across a wide range of temperatures was investigated on the surface of three porous carbon adsorbents with complementary structural properties. The measured adsorption equilibria were analyzed using a method that can accurately account for nonideal fluid properties and distinguish between absolute and excess quantities of adsorption, and that also allows the direct calculation of the thermodynamic potentials relevant to adsorption. On zeolite-templated carbon (ZTC), a material that exhibits extremely high surface area with optimal pore size and homogeneous structure, methane adsorption occurs with unusual thermodynamic properties that are greatly beneficial for deliverable gas storage: an enthalpy of adsorption that increases with site occupancy, and an unusually low entropy of the adsorbed phase. The origin of these properties is elucidated by comparison of the experimental results with a statistical mechanical model. The results indicate that temperature-dependent clustering (i.e., reduced configurations) of the adsorbed phase due to enhanced lateral interactions can account for the peculiarities of methane adsorbed on ZTC.", "doi": "10.1021/acs.jpcc.5b05021", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2015-11-26", "series_number": "47", "volume": "119", "issue": "47", "pages": "26409-26421" }, { "id": "authors:cv9pp-has19", "collection": "authors", "collection_id": "cv9pp-has19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150511-083811430", "type": "article", "title": "Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion, and its stabilization of rutile TiO_2", "author": [ { "family_name": "Lan", "given_name": "Tian", "clpid": "Lan-Tian" }, { "family_name": "Li", "given_name": "C. W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Smith", "given_name": "H.", "clpid": "Smith-Hillary-L" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Although the rutile structure of TiO_2 is stable at high temperatures, the conventional quasiharmonic approximation predicts that several acoustic phonons decrease anomalously to zero frequency with thermal expansion, incorrectly predicting a structural collapse at temperatures well below 1000 K. Inelastic neutron scattering was used to measure the temperature dependence of the phonon density of states (DOS) of rutile TiO_2 from 300 to 1373 K. Surprisingly, these anomalous acoustic phonons were found to increase in frequency with temperature. First-principles calculations showed that with lattice expansion, the potentials for the anomalous acoustic phonons transform from quadratic to quartic, stabilizing the rutile phase at high temperatures. In these modes, the vibrational displacements of adjacent Ti and O atoms cause variations in hybridization of 3d electrons of Ti and 2p electrons of O atoms. With thermal expansion, the energy variation in this \"phonon-tracked hybridization\" flattens the bottom of the interatomic potential well between Ti and O atoms, and induces a quarticity in the phonon potential.", "doi": "10.1103/PhysRevB.92.054304", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2015-08-01", "series_number": "5", "volume": "92", "issue": "5", "pages": "Art. No. 054304" }, { "id": "authors:s7myy-ydy82", "collection": "authors", "collection_id": "s7myy-ydy82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150825-112310788", "type": "article", "title": "Structure of the high voltage phase of layered P2-Na_(2/3\u2212z)[Mn_(1/2)Fe_(1/2)]O_2 and the positive effect of Ni substitution on its stability", "author": [ { "family_name": "Talaie", "given_name": "Elahe", "clpid": "Talaie-Elahe" }, { "family_name": "Duffort", "given_name": "Victor", "clpid": "Duffort-Victor" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Nazar", "given_name": "Linda F.", "clpid": "Nazar-L-F" } ], "abstract": "A combination of operando X-ray diffraction, pair distribution function (PDF) analysis coupled with electrochemical measurements and M\u00f6ssbauer spectroscopy elucidates the nature of the phase transitions induced by insertion and extraction of sodium ions in P2-Na_(0.67)[Ni_yMn_(0.5+y)Fe_(0.5\u22122y)]O_2 (y = 0, 0.10, 0.15). When phase transitions are avoided, the optimal cathode material \u2013 P2-Na_(0.67)Fe_(0.2)Mn_(0.65)Ni_(0.15)O_2 \u2013 delivers 25% more energy than the unsubstituted material, sustaining high specific energy (350 Wh kg^(\u22121)) at moderate rates and maintains 80% of the original energy density after 150 cycles \u2013 a significant improvement in performance vs. the unsubstituted analogue. The crystal structure of the high voltage phase is solved for the first time by X-ray PDF analysis of P2-Na_(0.67\u2212z)Fe_(0.5)Mn_(0.5)O_2 (where z \u223c 0.5), revealing that migration of the transition metals \u2013 particularly Fe^(3+) \u2013 into tetrahedral sites in the interlayer space occurs at high potential. This results in new short range order between two adjacent layers. Although the transition metal migration is reversible as proven by electrochemical performance, it induces a large disfavourable cell polarization. The deleterious high voltage transition is mitigated by substitution of Fe^(3+) by Mn^(4+)/Ni^(2+), giving rise to better cycling performance. Moreover, as demonstrated by ^(57)Fe M\u00f6ssbauer spectroscopy, the much lower ratio of Fe^(4+)O_6 to Fe^(3+)O_6 observed systematically across the range of Ni content \u2013 compared to the values expected from a purely ionic model \u2013 suggests redox activity involves the O-2p orbitals owing to their overlap with the transition metal-3d orbitals.", "doi": "10.1039/c5ee01365h", "issn": "1754-5692", "publisher": "Royal Society of Chemistry", "publication": "Energy and Environmental Science", "publication_date": "2015-08-01", "series_number": "8", "volume": "8", "issue": "8", "pages": "2512-2523" }, { "id": "authors:e909x-gy063", "collection": "authors", "collection_id": "e909x-gy063", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150720-083049878", "type": "article", "title": "Krypton Adsorption on Zeolite-Templated Carbon and Anomalous Surface Thermodynamics", "author": [ { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Krypton adsorption was measured at eight temperatures between 253 and 433 K on a zeolite-templated carbon and two commercial carbons. The data were fitted using a generalized Langmuir isotherm model and thermodynamic properties were extracted. Differing from that on commercial carbons, krypton adsorption on the zeolite-templated carbon is accompanied by an increasing isosteric enthalpy of adsorption, rising by up to 1.4 kJ mol^(\u20131) as a function of coverage. This increase is a result of enhanced adsorbate\u2013adsorbate interactions promoted by the ordered, nanostructured surface of the adsorbent. An assessment of the strength and nature of these adsorbate\u2013adsorbate interactions is made by comparing the measured isosteric enthalpies of adsorption (and other thermodynamic quantities) to fundamental metrics of intermolecular interactions of krypton and other common gases.", "doi": "10.1021/acs.langmuir.5b01497", "issn": "0743-7463", "publisher": "American Chemical Society", "publication": "Langmuir", "publication_date": "2015-07-28", "series_number": "29", "volume": "31", "issue": "29", "pages": "7991-7998" }, { "id": "authors:t3yky-p2q38", "collection": "authors", "collection_id": "t3yky-p2q38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150430-134245369", "type": "article", "title": "Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia", "author": [ { "family_name": "Li", "given_name": "C. W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Lan", "given_name": "T.", "clpid": "Lan-T" }, { "family_name": "Niedziela", "given_name": "J. L.", "orcid": "0000-0002-2990-923X", "clpid": "Niedziela-J-L" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Keith", "given_name": "J. B.", "clpid": "Keith-J-B" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering measurements on monoclinic zirconia (ZrO_2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373wK. Temperature-dependent phonon densities of states (DOS) are reported, as are Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Gr\u00fcneisen parameters. These mode Gr\u00fcneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhat more anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.", "doi": "10.1103/PhysRevB.91.144302", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2015-04-01", "series_number": "14", "volume": "91", "issue": "14", "pages": "Art. No. 144302" }, { "id": "authors:0wpxk-1ak81", "collection": "authors", "collection_id": "0wpxk-1ak81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150112-100734557", "type": "article", "title": "Observation and Investigation of Increasing Isosteric Heat of Adsorption of Ethane on Zeolite-Templated Carbon", "author": [ { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Ethane adsorption was measured on zeolite-templated carbon (ZTC) and compared to superactivated carbon MSC-30. Isotherms measured at temperatures between 252 and 423 K were fitted using a superposition of two Langmuir isotherms, and thermodynamic properties were assessed. Unlike typical carbon adsorbents, the isosteric heat of adsorption on ZTC increases by up to 4.6 kJ/mol with surface coverage. This increase is attributed to strong adsorbate\u2013adsorbate intermolecular interactions, a hypothesis that is shown to be consistent with fundamental estimates of intermolecular interactions. Furthermore, the molar entropy of the adsorbed phase was measured and compared to an estimate derived from statistical mechanics. While the measured and estimated entropies of the adsorbed phase of ethane on MSC-30 are in agreement, they differ significantly on ZTC at high coverage, indicative of the atypical properties of ethane adsorption on ZTC.", "doi": "10.1021/jp510991y", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2015-01-15", "series_number": "2", "volume": "119", "issue": "2", "pages": "944-950" }, { "id": "authors:67hvq-njk27", "collection": "authors", "collection_id": "67hvq-njk27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150303-083220958", "type": "article", "title": "Phonon anharmonicity in silicon from 100 to 1500 K", "author": [ { "family_name": "Kim", "given_name": "D. S.", "orcid": "0000-0002-5707-2609", "clpid": "Kim-Dennis-S" }, { "family_name": "Smith", "given_name": "H. L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Niedziela", "given_name": "J. L.", "orcid": "0000-0002-2990-923X", "clpid": "Niedziela-J-L" }, { "family_name": "Li", "given_name": "C. W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was performed on silicon powder to measure the phonon density of states (DOS) from 100 to 1500 K. The mean fractional energy shifts with temperature of the modes were \u27e8\u0394\u025b_i/\u025b_i\u0394T\u27e9=\u22120.07, giving a mean isobaric Gr\u00fcneisen parameter of +6.95\u00b10.67, which is significantly different from the isothermal parameter of +0.98. These large effects are beyond the predictions from quasiharmonic models using density functional theory or experimental data, demonstrating large effects from phonon anharmonicity. At 1500 K the anharmonicity contributes 0.15k_B/atom to the vibrational entropy, compared to 0.03k_B/atom from quasiharmonicity. Excellent agreement was found between the entropy from phonon DOS measurements and the reference NIST-JANAF thermodynamic entropy from calorimetric measurements.", "doi": "10.1103/PhysRevB.91.014307", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2015-01-01", "series_number": "1", "volume": "91", "issue": "1", "pages": "Art. No. 014307" }, { "id": "authors:rdp7j-6k404", "collection": "authors", "collection_id": "rdp7j-6k404", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141204-112837164", "type": "article", "title": "Temperature Dependent Magnon-Phonon Coupling in bcc Fe from Theory and Experiment", "author": [ { "family_name": "K\u00f6rmann", "given_name": "F.", "clpid": "K\u00f6rmann-F" }, { "family_name": "Grabowski", "given_name": "B.", "clpid": "Grabowski-B" }, { "family_name": "Dutta", "given_name": "B.", "clpid": "Dutta-B" }, { "family_name": "Hickel", "given_name": "T.", "clpid": "Hickel-T" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Neugebauer", "given_name": "J.", "clpid": "Neugebauer-J" } ], "abstract": "An ab initio based framework for quantitatively assessing the phonon contribution due to magnon-phonon interactions and lattice expansion is developed. The theoretical results for bcc Fe are in very good agreement with high-quality phonon frequency measurements. For some phonon branches, the magnon-phonon interaction is an order of magnitude larger than the phonon shift due to lattice expansion, demonstrating the strong impact of magnetic short-range order even significantly above the Curie temperature. The framework closes the previous simulation gap between the ferro- and paramagnetic limits.", "doi": "10.1103/PhysRevLett.113.165503", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2014-10-14", "series_number": "16", "volume": "113", "issue": "16", "pages": "Art. No. 165503" }, { "id": "authors:wnrv1-sd923", "collection": "authors", "collection_id": "wnrv1-sd923", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140925-154322512", "type": "article", "title": "Neutron and X-Ray Studies of Advanced Materials VII: Challenges of the Future World: Foreword", "author": [ { "family_name": "Barabash", "given_name": "R. I.", "clpid": "Barabash-R-I" }, { "family_name": "Kostorz", "given_name": "G.", "clpid": "Kostorz-G" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" } ], "abstract": "The selection of the manuscripts in the special topic \"Neutron and X-ray Studies of Advanced Materials VII:\nChallenges of the Future World\" is based on the material presented during the TMS 2014 Annual Meeting February\n16 to 20, 2014, at the San Diego Convention Center in San Diego, California.\nThe United Nations Education, Science and Culture Organization (UNESCO) declared 2014 the International Year of\nCrystallography to acknowledge the importance of the first theoretical predictions (M. Laue) and brilliant\nexperimental verification of diffraction phenomena (W. Friedrich and P. Knipping) more than a century ago. During\nthis century the diffraction theory and experimental techniques were immensely developed. Diffraction entered our\neveryday life including important medical, technological, industrial, and scientific applications. The significance of the\ndiffraction techniques continued to increase in the past 100 years.\nThe aim of the symposium was to provide a forum for discussion of using state-of-the-art neutron and X-ray scattering\ntechniques to probe advanced materials.", "doi": "10.1007/s11661-014-2479-7", "issn": "1073-5623", "publisher": "Springer", "publication": "Metallurgical and Materials Transactions A", "publication_date": "2014-10", "series_number": "11", "volume": "45A", "issue": "11", "pages": "4770-4771" }, { "id": "authors:txqzg-aa896", "collection": "authors", "collection_id": "txqzg-aa896", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141016-125243303", "type": "article", "title": "Polaron-ion correlations in Li_xFePO_4 studied by x-ray nuclear resonant forward scattering at elevated pressure and temperature", "author": [ { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-H-J" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Valence fluctuations of Fe^(2+) and Fe^(3+) were studied in a solid solution of Li_xFePO_4 by nuclear resonant forward scattering of synchrotron x rays while the sample was heated in a diamond-anvil pressure cell. The spectra acquired at different temperatures and pressures were analyzed for the frequencies of valence changes using the Blume-Tjon model of a system with a fluctuating Hamiltonian. These frequencies were analyzed to obtain activation enthalpies and an activation volume for polaron hopping. There was a large suppression of hopping frequency with pressure, giving an activation volume for polaron hopping of 5.8\u00b10.7 \u00c5^ 3. This large, positive value is typical of ion diffusion, which indicates correlated motions of polarons and Li^+ ions that alter the dynamics of both. Monte Carlo simulations were used to estimate the strength of the polaron-ion interaction energy.", "doi": "10.1103/PhysRevB.90.094303", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2014-09-12", "series_number": "9", "volume": "90", "issue": "9", "pages": "Art. No. 094303" }, { "id": "authors:5e4t4-q0452", "collection": "authors", "collection_id": "5e4t4-q0452", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141121-135832086", "type": "article", "title": "Nonharmonic phonons in \u03b1-iron at high temperatures", "author": [ { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "Paul", "clpid": "Chow-Paul" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Phonon densities of states (DOS) of bcc \u03b1\u2212^(57)Fe were measured from room temperature through the 1044 K Curie transition and the 1185 K fcc \u03b3-Fe phase transition using nuclear resonant inelastic x-ray scattering. At higher temperatures all phonons shift to lower energies (soften) with thermal expansion, but the low transverse modes soften especially rapidly above 700 K, showing strongly nonharmonic behavior that persists through the magnetic transition. Interatomic force constants for the bcc phase were obtained by iteratively fitting a Born\u2013von K\u00e1rm\u00e1n model to the experimental phonon spectra using a genetic algorithm optimization. The second-nearest-neighbor fitted axial force constants weakened significantly at elevated temperatures. An unusually large nonharmonic behavior is reported, which increases the vibrational entropy and accounts for a contribution of 35 meV/atom in the free energy at high temperatures. The nonharmonic contribution to the vibrational entropy follows the thermal trend of the magnetic entropy, and may be coupled to magnetic excitations. A small change in vibrational entropy across the \u03b1\u2212\u03b3 structural phase transformation is also reported.", "doi": "10.1103/PhysRevB.90.064303", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2014-08-01", "series_number": "6", "volume": "90", "issue": "6", "pages": "Art. No. 064303" }, { "id": "authors:htdj3-g4651", "collection": "authors", "collection_id": "htdj3-g4651", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140224-090219387", "type": "article", "title": "Anharmonic lattice dynamics of Ag_2O studied by inelastic neutron scattering and first principles molecular dynamics simulations", "author": [ { "family_name": "Lan", "given_name": "Tian", "clpid": "Lan-Tian" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Niedziela", "given_name": "J. L.", "orcid": "0000-0002-2990-923X", "clpid": "Niedziela-J-L" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Abernathy", "given_name": "Douglas L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering measurements on silver oxide (Ag_2O) with the cuprite structure were\nPerformed at temperatures from40 to 400 K, and Fourier transform far-infrared spectra were measured\nFrom 100 to 300K. The measured phonon densities of states and the infrared spectra showed unusually\nlarge energy shifts with temperature, and large linewidth broadenings. First principles molecular\ndynamics (MD) calculations were performed at various temperatures, successfully accounting for\nthe negative thermal expansion (NTE) and local dynamics. Using the Fourier-transformed velocity\nautocorrelation method, the MD calculations reproduced the large anharmonic effects of Ag_2O, and\nwere in excellent agreement with the neutron scattering data. The quasiharmonic approximation\n(QHA) was less successful in accounting for much of the phonon behavior. The QHA could account\nfor some of the NTE below 250 K, although not at higher temperatures. Strong anharmonic effects\nwere found for both phonons and for the NTE. The lifetime broadenings of Ag_2O were explained by\nanharmonic perturbation theory, which showed rich interactions between the Ag-dominated modes\nand the O-dominated modes in both up- and down-conversion processes.", "doi": "10.1103/PhysRevB.89.054306", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2014-02-01", "series_number": "5", "volume": "89", "issue": "5", "pages": "Art. No. 054306" }, { "id": "authors:jsmb4-e5r94", "collection": "authors", "collection_id": "jsmb4-e5r94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140129-130314711", "type": "article", "title": "Spin-State Effects on the Thermal Dihydrogen Release from Solid-State [MH(\u03b7^2\u2011H_2)dppe_2]^+ (M = Fe, Ru, Os) Organometallic Complexes for Hydrogen Storage Applications", "author": [ { "family_name": "Abrecht", "given_name": "David G.", "clpid": "Abrecht-D-G" }, { "family_name": "Mu\u00f1oz", "given_name": "Jorge A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "M\u00f6ssbauer spectroscopy, experimental thermodynamic measurements, and computational studies were performed to investigate the properties of molecular hydrogen binding to the organometallic fragments [MHdppe_2]^+ (M = Fe, Ru, Os; dppe =1,2-bis(diphenylphosphino)ethane) to form the dihydrogen complex fragments [MH(\u03b7^2-H_2)dppe_2]^+. M\u00f6ssbauer spectroscopy showed that the dehydrogenated complex [FeHdppe_2]^+ adopts a geometry consistent with the triplet spin state, transitioning to a singlet state complex upon addition of the dihydrogen molecule in a manner similar to the previously studied dinitrogen complexes. From simulations, this spin transition behavior was found to be responsible for the strong binding behavior experimentally observed in the iron complex. Spin-singlet to spin-singlet transitions were found to exhibit thermodynamics consistent with the 5d > 3d > 4d binding trend observed for other transition metal dihydrogen complexes. Finally, the method for distinguishing between dihydrogen and dihydride complexes based on partial quadrupole splittings observed in M\u00f6ssbauer spectra was confirmed, providing a tool for further characterization of these unique species for M\u00f6ssbauer active compounds.", "doi": "10.1021/jp409739b", "pmcid": "PMC3983317", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2014-01-30", "series_number": "4", "volume": "118", "issue": "4", "pages": "1783-1792" }, { "id": "authors:2fnr5-e8b36", "collection": "authors", "collection_id": "2fnr5-e8b36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140407-104908427", "type": "article", "title": "Electrochemical Cycling and Lithium Insertion in Nanostructured FeF_3 Cathodes", "author": [ { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-H-J" }, { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Kim", "given_name": "L.", "clpid": "Kim-L" }, { "family_name": "Harding", "given_name": "Trina K.", "clpid": "Harding-T-K" }, { "family_name": "Jones", "given_name": "Simon C.", "orcid": "0000-0002-1952-3720", "clpid": "Jones-S-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The cycle lives for cathodes of nanocrystalline iron trifluoride (FeF_3) were measured in rechargeable lithium batteries at different depths of discharge. When the discharge was limited to less than one Li^+ ion per FeF_3, both the cycle life and energy efficiency were considerably greater than when converting FeF_3 into Fe and LiF in deep discharge. An in situ X-ray diffractometry (XRD) study of the FeF_3 cathode during its initial discharge to LiFeF_3 showed a continuous change of the FeF_3 diffraction pattern, indicating Li^+ insertion into the rhombohedral FeF_3 causing distortion of its lattice parameters. Electrochemical cycling is most reversible when this mechanism occurs in the absence of other changes in the crystal structure.", "doi": "10.1149/2.096403jes", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2014-01-16", "series_number": "3", "volume": "161", "issue": "3", "pages": "A445-A449" }, { "id": "authors:6jyya-nkh13", "collection": "authors", "collection_id": "6jyya-nkh13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140327-132950189", "type": "article", "title": "Neutron and X-ray Studies of Advanced Materials VI: Diffraction Centennial and Beyond", "author": [ { "family_name": "Barabash", "given_name": "R. I.", "clpid": "Barabash-R-I" }, { "family_name": "Kostorz", "given_name": "G.", "clpid": "Kostorz-G" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" } ], "abstract": "The selection of the manuscripts in the special topic \"Neutron and X-ray Diffraction Studies of Advanced Materials VI: Centennial and Beyond\" is based on the material presented during the TMS 2013 Annual Meeting, March 3 to 7, 2013, in San Antonio, Texas, USA.", "doi": "10.1007/s11661-013-2031-1", "issn": "1073-5623", "publisher": "Springer", "publication": "Metallurgical and Material Transactions A", "publication_date": "2014-01", "series_number": "1", "volume": "45A", "issue": "1", "pages": "72-74" }, { "id": "authors:qsbhc-pzm47", "collection": "authors", "collection_id": "qsbhc-pzm47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140311-093847567", "type": "article", "title": "Thermodynamic modelling of crystalline unary phases", "author": [ { "family_name": "Palumbo", "given_name": "M.", "clpid": "Palumbo-M" }, { "family_name": "Burton", "given_name": "B.", "clpid": "Burton-B" }, { "family_name": "Costa e Silva", "given_name": "A.", "clpid": "Costa-e-Silva-A" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Grabowski", "given_name": "B.", "clpid": "Grabowski-B" }, { "family_name": "Grimvall", "given_name": "G.", "clpid": "Grimball-G" }, { "family_name": "Hallstedt", "given_name": "B.", "clpid": "Hallstedt-B" }, { "family_name": "Hellman", "given_name": "O.", "orcid": "0000-0002-3453-2975", "clpid": "Hellman-Olle" }, { "family_name": "Lindahl", "given_name": "B.", "clpid": "Lindahl-B" }, { "family_name": "Schneider", "given_name": "A.", "clpid": "Schneider-A" }, { "family_name": "Turchi", "given_name": "P. E. A.", "clpid": "Turchi-P-E-A" }, { "family_name": "Xiong", "given_name": "W.", "clpid": "Xiong-W" } ], "abstract": "Progress in materials science through thermodynamic modelling may rest crucially on access to a database, such as that developed by Scientific Group Thermodata Europe (SGTE) around 1990. It gives the Gibbs energy G(T)of the elements in the form of series as a function of temperature, i.e. essentially a curve fitting to experimental data. In the light of progress in theoretical understanding and first-principles calculation methods, the possibility for an improved database description of the thermodynamics of the elements has become evident. It is the purpose of this paper to provide a framework for such work. Lattice vibrations, which usually give the major contribution to G(T), are treated in some detail with a discussion of neutron scattering studies of anharmonicity in aluminium, first-principles calculations including ab initio molecular dynamics (AIMD), and the strength and weakness of analytic model representations of data. Similarly, electronic contributions to G(T) are treated on the basis of the density of states N(E) for metals, with emphasis on effects at high T. Further, we consider G(T) below 300\u2009K, which is not covered by SGTE. Other parts in the paper discuss metastable and dynamically unstable lattices, G(T) in the region of superheated solids and the requirement on a database in the calculation of phase diagrams.", "doi": "10.1002/pssb.201350133", "issn": "0370-1972", "publisher": "Wiley", "publication": "Physica Status Solidi B", "publication_date": "2014-01", "series_number": "1", "volume": "251", "issue": "1", "pages": "14-32" }, { "id": "authors:264jk-61004", "collection": "authors", "collection_id": "264jk-61004", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140103-082148707", "type": "article", "title": "Changes in vibrational entropy during the early stages of chemical unmixing in fcc Cu\u20136% Fe", "author": [ { "family_name": "Smith", "given_name": "Hillary L.", "clpid": "Smith-Hillary-L" }, { "family_name": "Hornbuckle", "given_name": "B. C.", "clpid": "Hornbuckle-B-C" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Fu", "given_name": "B.", "clpid": "Fu-B" }, { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Thompson", "given_name": "G. B.", "clpid": "Thompson-G-B" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Xiao", "given_name": "Y.", "clpid": "Xiao-Yuming" }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169", "clpid": "Hu-Michael-Y" }, { "family_name": "Zhao", "given_name": "J.", "orcid": "0000-0002-0777-3626", "clpid": "Zhao-Jiyong" }, { "family_name": "Alp", "given_name": "E. Ercan", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A nanocrystalline face-centered cubic (fcc) solid solution of 6% Fe in Cu was prepared by high-energy ball milling, and annealed at temperatures from 200 to 360 \u00b0C to induce chemical unmixing. The chemical state of the material was characterized by three-dimensional atom probe microscopy, M\u00f6ssbauer spectrometry and X-ray powder diffractometry. The unmixing was heterogeneous, with iron atoms forming iron-rich zones that thicken with further annealing. The phonon partial density of states (pDOS) of ^(57)Fe was measured by nuclear resonant inelastic X-ray scattering, showing the pDOS of the as-prepared material to be that of an fcc crystal. The features of this pDOS became broader in the early stages of unmixing, but only small changes in average phonon frequencies occurred until the body-centered cubic (bcc) phase began to form. The vibrational entropy calculated from the pDOS underwent little change during the early stage of annealing, but decreased rapidly when the bcc phase formed in the material.", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2013-11", "series_number": "19", "volume": "61", "issue": "19", "pages": "7466-7472" }, { "id": "authors:nhf3w-fgs10", "collection": "authors", "collection_id": "nhf3w-fgs10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130627-095811994", "type": "article", "title": "Phonon densities of states of face-centered-cubic Ni-Fe alloys", "author": [ { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Horwath", "given_name": "J.", "clpid": "Horwath-J" }, { "family_name": "Semiatin", "given_name": "S. L.", "clpid": "Semiatin-S-L" }, { "family_name": "Leontsev", "given_name": "S. O.", "clpid": "Leontsev-S-O" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "Paul", "clpid": "Chow-Paul" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to determine the phonon densities of states of face-centered-cubic Ni-Fe alloys. Increasing Fe concentration results in an average softening of the phonon modes. Chemical ordering of the Ni_(0.72)Fe_(0.28) alloy results in a reduction of the partial vibrational entropy of the Fe atoms but does not significantly change the partial vibrational entropy of the Ni atoms. Changes in the phonon densities of states with composition and chemical ordering are discussed and analyzed with a cluster expansion method.", "doi": "10.1063/1.4794354", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2013-05-07", "series_number": "17", "volume": "113", "issue": "17", "pages": "Art. No. 17A308" }, { "id": "authors:9xvn8-32x79", "collection": "authors", "collection_id": "9xvn8-32x79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130305-085444971", "type": "article", "title": "Anomalous Isosteric Enthalpy of Adsorption of Methane on Zeolite-Templated Carbon", "author": [ { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Murialdo", "given_name": "Maxwell", "clpid": "Murialdo-M" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A thermodynamic study of the enthalpy of adsorption of methane on high surface area carbonaceous materials was carried out from 238 to 526 K. The absolute quantity of adsorbed methane as a function of equilibrium pressure was determined by fitting isotherms to a generalized Langmuir-type equation. Adsorption of methane on zeolite-templated carbon, an extremely high surface area material with a periodic arrangement of narrow micropores, shows an increase in isosteric enthalpy with methane occupancy; i.e., binding energies are greater as adsorption quantity increases. The heat of adsorption rises from 14 to 15 kJ/mol at near-ambient temperature and then falls to lower values at very high loading (above a relative site occupancy of 0.7), indicating that methane/methane interactions within the adsorption layer become significant. The effect seems to be enhanced by a narrow pore-size distribution centered at 1.2 nm, approximately the width of two monolayers of methane, and reversible methane delivery increases by up to 20% over MSC-30 at temperatures and pressures near ambient.", "doi": "10.1021/ja311415m", "issn": "0002-7863", "publisher": "American Chemical Society", "publication": "Journal of the American Chemical Society", "publication_date": "2013-01-23", "series_number": "3", "volume": "135", "issue": "3", "pages": "990-993" }, { "id": "authors:mkb5c-eq263", "collection": "authors", "collection_id": "mkb5c-eq263", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130211-115651354", "type": "article", "title": "Electronic structure and vibrational entropies of fcc Au-Fe alloys", "author": [ { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Horwath", "given_name": "J.", "clpid": "Horwath-J" }, { "family_name": "Semiatin", "given_name": "S. L.", "clpid": "Semiatin-S-L" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "Paul", "clpid": "Chow-Paul" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Phonon density of states (DOS) curves were measured on alloys of face-centered-cubic (fcc) Au-Fe using nuclear resonant inelastic x-ray scattering (NRIXS) and inelastic neutron scattering (INS). The NRIXS and INS results were combined to obtain the total phonon DOS and the partial phonon DOS curves of Au and Fe atoms from which vibrational entropies were calculated. The main effect on the vibrational entropy of alloying comes from a stiffening of the Au partial phonon DOS with Fe concentration. Force constants were calculated from first principles for several compositions and show a local stiffening of Au-Au bonds close to Fe atoms. The calculated phonon DOS curves reproduce the experimental trend. The stiffening is attributed to two main effects comparable in magnitude: (i) an increase in electron density in the free-electron-like states and (ii) stronger sd hybridization.", "doi": "10.1103/PhysRevB.87.014301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2013-01-01", "series_number": "1", "volume": "87", "issue": "1", "pages": "Art. No. 014301" }, { "id": "authors:4g7n5-w2a30", "collection": "authors", "collection_id": "4g7n5-w2a30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130221-101931390", "type": "article", "title": "Neutron and X-Ray Studies of Advanced Materials V - Diffraction Centennial - Foreword", "author": [ { "family_name": "Barabash", "given_name": "R. I.", "clpid": "Barabash-R-I" }, { "family_name": "Wang", "given_name": "Xun-Li", "clpid": "Wang-Xun-Li" }, { "family_name": "Korstorz", "given_name": "G.", "clpid": "Korstorz-G" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Levine", "given_name": "Lyle", "clpid": "Levine-L" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" } ], "abstract": "The selection of the manuscripts in the special topic \"Neutron and X-Ray Diffraction Studies of Advanced Materials\nV\u2014Centennial\" is based on the materials presented during the TMS 2012 Annual Meeting 03/11/2012\u201303/15/2012,\nOrlando, FL, USA.", "doi": "10.1007/s11661-012-1499-4", "issn": "1073-5623", "publisher": "Springer", "publication": "Metallurgical and Materials Transactions A", "publication_date": "2013-01", "series_number": "1", "volume": "44", "issue": "1", "pages": "15-16" }, { "id": "authors:6gn0j-ze137", "collection": "authors", "collection_id": "6gn0j-ze137", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130124-084248748", "type": "article", "title": "Hydrogen diffusion in potassium intercalated graphite studied by quasielastic neutron scattering", "author": [ { "family_name": "Purewal", "given_name": "Justin", "clpid": "Purewal-J-J" }, { "family_name": "Keith", "given_name": "J. Brandon", "clpid": "Keith-J-B" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Brown", "given_name": "Craig M.", "clpid": "Brown-C-M" }, { "family_name": "Tyagi", "given_name": "Madhusudan", "clpid": "Tyagi-M" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The graphite intercalation compound KC24 adsorbs hydrogen gas at low temperatures up to a maximum stoichiometry of KC_(24)(H_2)_2, with a differential enthalpy of adsorption of approximately \u22129 kJ\u2009mol^(\u22121). The hydrogen molecules and potassium atoms form a two-dimensional condensed phase between the graphite layers. Steric barriers and strong adsorption potentials are expected to strongly hinder hydrogen diffusion within the host KC_24 structure. In this study, self-diffusion in a KC_(24)(H_2)_0.5 sample is measured experimentally by quasielastic neutron scattering and compared to values from molecular dynamics simulations. Self-diffusion coefficients are determined by fits of the experimental spectra to a honeycomb net diffusion model and found to agree well with the simulated values. The experimental H2 diffusion coefficients in KC_24 vary from 3.6 \u00d7 10^(\u22129) m^2\u2009s^(\u22121) at 80 K to 8.5 \u00d7 10^(\u22129) m^2\u2009s^(\u22121) at 110 K. The measured diffusivities are roughly an order of magnitude lower that those observed on carbon adsorbents, but compare well with the rate of hydrogen self-diffusion in molecular sieve zeolites.", "doi": "10.1063/1.4767055", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "2012-12-14", "series_number": "22", "volume": "137", "issue": "22", "pages": "Art. No. 224704" }, { "id": "authors:65898-qt590", "collection": "authors", "collection_id": "65898-qt590", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121127-143917563", "type": "article", "title": "Evaluation of the Thermodynamic Properties of H_2 Binding in Solid State Dihydrogen Complexes [M(\u03b7^2\u2011H_2)(CO)dppe_2][BArF^(24)] (M = Mn, Tc, Re): An Experimental and First Principles Study", "author": [ { "family_name": "Abrecht", "given_name": "David G.", "clpid": "Abrecht-D-G" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The solid state complex [Mn(CO)dppe_2][BArF^(24)] was synthesized, and the thermodynamic behavior and properties of the hydrogen absorption reaction to form the dihydrogen complex [Mn(\u03b7^2-H_2)dppe_2][BArF^(24)] were measured over the temperature range 313\u2013373 K and pressure range 0\u2013600 Torr using the Sieverts method. The absorption behavior was accurately described by Langmuir isotherms, and enthalpy and entropy values of \u0394H\u00b0 = \u221252.2 kJ/mol and \u0394S\u00b0 = \u221299.6 J/(mol K) for the absorption reaction were obtained from the Langmuir equilibrium constant. The observed binding strength was similar to metal hydrides and other organometallic complexes, despite rapid kinetics suggesting a site-binding mechanism similar to physisorption materials. Electronic structure calculations using the LANL2DZ-ECP basis set were performed for hydrogen absorption over the organometallic fragments [M(CO)dppe_2]^+ (M = Mn, Tc, Re). Langmuir isotherms derived from calculation for absorption onto the manganese fragment successfully simulated both the pressure\u2013composition behavior and thermodynamic properties obtained from experiment. Results from calculations for the substitution of the metal center reproduced qualitative binding strength trends of 5d > 3d > 4d previously reported for the group 6 metals.", "doi": "10.1021/jp308176f", "pmcid": "PMC3521573", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2012-10-25", "series_number": "42", "volume": "116", "issue": "42", "pages": "22245-22252" }, { "id": "authors:kkjzh-6nm47", "collection": "authors", "collection_id": "kkjzh-6nm47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121115-091306052", "type": "article", "title": "Phonon anharmonicity of rutile SnO_2 studied by Raman spectrometry and first principles calculations of the kinematics of phonon-phonon interactions", "author": [ { "family_name": "Lan", "given_name": "Tian", "clpid": "Lan-Tian" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Raman spectra of rutile tin dioxide (SnO_2) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The B_(2g) mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the B_(2g) mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.", "doi": "10.1103/PhysRevB.86.134302", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2012-10-11", "series_number": "13", "volume": "86", "issue": "13", "pages": "Art. No. 134302" }, { "id": "authors:dwf2q-df743", "collection": "authors", "collection_id": "dwf2q-df743", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120730-135435074", "type": "article", "title": "Zeolite-Templated Carbon Materials for High-Pressure Hydrogen Storage", "author": [ { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Vajo", "given_name": "John J.", "orcid": "0000-0002-6271-4899", "clpid": "Vajo-J-J" }, { "family_name": "Cumberland", "given_name": "Robert W.", "clpid": "Cumberland-R-W" }, { "family_name": "Wilson", "given_name": "Andrew A.", "clpid": "Wilson-A-A" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Zeolite-templated carbon (ZTC) materials were synthesized, characterized, and evaluated as potential hydrogen storage materials between 77 and 298 K up to 30 MPa. Successful synthesis of high template fidelity ZTCs was confirmed by X-ray diffraction and nitrogen adsorption at 77 K; BET surface areas up to ~3600 mT2 g^(\u20131) were achieved. Equilibrium hydrogen adsorption capacity in ZTCs is higher than all other materials studied, including superactivated carbon MSC-30. The ZTCs showed a maximum in Gibbs surface excess uptake of 28.6 mmol g\u20131 (5.5 wt %) at 77 K, with hydrogen uptake capacity at 300 K linearly proportional to BET surface area: 2.3 mmol g^(\u20131) (0.46 wt %) uptake per 1000 m^2 g^(\u20131) at 30 MPa. This is the same trend as for other carbonaceous materials, implying that the nature of high-pressure adsorption in ZTCs is not unique despite their narrow microporosity and significantly lower skeletal densities. Isoexcess enthalpies of adsorption are calculated between 77 and 298 K and found to be 6.5\u20136.6 kJ mol^(\u20131) in the Henry's law limit.", "doi": "10.1021/la302050m", "issn": "0743-7463", "publisher": "American Chemical Society", "publication": "Langmuir", "publication_date": "2012-06-03", "series_number": "26", "volume": "28", "issue": "26", "pages": "10057-10063" }, { "id": "authors:yx81b-qkq12", "collection": "authors", "collection_id": "yx81b-qkq12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120501-074225382", "type": "article", "title": "Special Topic on \"Neutron and X-Ray Diffraction Studies of Advanced Materials IV\"", "author": [ { "family_name": "Barabash", "given_name": "R. I.", "clpid": "Barabash-R-I" }, { "family_name": "Wang", "given_name": "Xun-Li", "clpid": "Wang-Xun-Li" }, { "family_name": "Tiley", "given_name": "Jaimie", "clpid": "Tiley-J" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "N/A", "doi": "10.1007/s11661-011-0985-4", "issn": "1073-5623", "publisher": "Springer", "publication": "Metallurgical and Materials Transactions A", "publication_date": "2012-05", "series_number": "5", "volume": "43A", "issue": "5", "pages": "1410-1412" }, { "id": "authors:pa7bx-byk17", "collection": "authors", "collection_id": "pa7bx-byk17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120420-110715976", "type": "article", "title": "Phonon anharmonicity of rutile TiO_2 studied by Raman spectrometry and molecular dynamics simulations", "author": [ { "family_name": "Lan", "given_name": "Tian", "clpid": "Lan-Tian" }, { "family_name": "Tang", "given_name": "Xiaoli", "clpid": "Tang-Xiaoli" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Raman spectra of rutile titanium dioxide (TiO_2) were measured at temperatures from 100 to 1150 K. Each Raman mode showed unique changes with temperature. Beyond the volume-dependent quasiharmonicity, the explicit anharmonicity was large. A new method was developed to fit the thermal broadenings and shifts of Raman peaks with a full calculation of the kinematics of three-phonon and four-phonon processes, allowing the cubic and quartic components of the anharmonicity to be identified for each Raman mode. A dominant role of phonon-phonon kinematics on phonon shifts and broadenings is reported. Force-field molecular dynamics calculations with the Fourier-transformed velocity autocorrelation method were also used to perform a quantitative study of anharmonic effects, successfully accounting for the anomalous phonon anharmonicity of the B_1_(g) mode.", "doi": "10.1103/PhysRevB.85.094305", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2012-03-27", "series_number": "9", "volume": "85", "issue": "9", "pages": "Art. No. 094305" }, { "id": "authors:fj6tv-3by48", "collection": "authors", "collection_id": "fj6tv-3by48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120402-071927973", "type": "article", "title": "Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source", "author": [ { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Stone", "given_name": "B. M.", "clpid": "Stone-B-M" }, { "family_name": "Loguillo", "given_name": "M. J.", "clpid": "Loguillo-M-J" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Tang", "given_name": "X.", "clpid": "Tang-Xiaoli" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source (SNS) is optimized to provide a high neutron flux at the sample position with a large solid angle of detector coverage. The instrument incorporates modern neutron instrumentation, such as an elliptically focused neutron guide, high speed magnetic bearing choppers, and a massive array of ^3He linear position sensitive detectors. Novel features of the spectrometer include the use of a large gate valve between the sample and detector vacuum chambers and the placement of the detectors within the vacuum, both of which provide a window-free final flight path to minimize background scattering while allowing rapid changing of the sample and sample environment equipment. ARCS views the SNS decoupled ambient temperature water moderator, using neutrons with incident energy typically in the range from 15 to 1500 meV. This range, coupled with the large detector coverage, allows a wide variety of studies of excitations in condensed matter, such as lattice dynamics and magnetism, in both powder and single-crystal samples. Comparisons of early results to both analytical and Monte Carlo simulation of the instrument performance demonstrate that the instrument is operating as expected and its neutronic performance is understood. ARCS is currently in the SNS user program and continues to improve its scientific productivity by incorporating new instrumentation to increase the range of science covered and improve its effectiveness in data collection.", "doi": "10.1063/1.3680104", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "2012-01", "series_number": "1", "volume": "83", "issue": "1", "pages": "Art. No. 015114" }, { "id": "authors:2mnh5-z3c09", "collection": "authors", "collection_id": "2mnh5-z3c09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111212-121400317", "type": "article", "title": "Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of Cubic ScF_3", "author": [ { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Tang", "given_name": "Xiaoli", "clpid": "Tang-Xiaoli" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Keith", "given_name": "J. B.", "clpid": "Keith-J-B" }, { "family_name": "Tracy", "given_name": "S. J.", "clpid": "Tracy-S-J" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Cubic scandium trifluoride (ScF_3) has a large negative thermal expansion over a wide range of temperatures. Inelastic neutron scattering experiments were performed to study the temperature dependence of the lattice dynamics of ScF3 from 7 to 750 K. The measured phonon densities of states show a large anharmonic contribution with a thermal stiffening of modes around 25 meV. Phonon calculations with first-principles methods identified the individual modes in the densities of states, and frozen phonon calculations showed that some of the modes with motions of F atoms transverse to their bond direction behave as quantum quartic oscillators. The quartic potential originates from harmonic interatomic forces in the DO_9 structure of ScF_3, and accounts for phonon stiffening with the temperature and a significant part of the negative thermal expansion.", "doi": "10.1103/PhysRevLett.107.195504", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2011-11-04", "series_number": "19", "volume": "107", "issue": "19", "pages": "195504" }, { "id": "authors:h74bx-zbv49", "collection": "authors", "collection_id": "h74bx-zbv49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110928-101310590", "type": "article", "title": "Positive Vibrational Entropy of Chemical Ordering in FeV", "author": [ { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Winterrose", "given_name": "M. L.", "clpid": "Winterrose-M-L" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Sheets", "given_name": "A. O.", "clpid": "Sheets-A-O" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "Paul", "clpid": "Chow-Paul" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to measure phonon spectra of FeV as a B2 ordered compound and as a bcc solid solution. The two data sets were combined to give an accurate phonon density of states, and the phonon partial densities of states for V and Fe atoms. Contrary to the behavior of ordering alloys studied to date, the phonons in the B2 ordered phase are softer than in the solid solution. Ordering increases the vibrational entropy by +0.22\u00b10.03k_B/atom, which stabilizes the ordered phase to higher temperatures. First-principles calculations show that the number of electronic states at the Fermi level increases upon ordering, enhancing the screening between ions, and reducing the interatomic force constants. The effect of screening is larger at the V atomic sites than at the Fe atomic sites.", "doi": "10.1103/PhysRevLett.107.115501", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2011-09-08", "series_number": "11", "volume": "107", "issue": "11", "pages": "Art. No. 115501" }, { "id": "authors:1zky1-dfz35", "collection": "authors", "collection_id": "1zky1-dfz35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110826-085225564", "type": "article", "title": "First-principles study of phonon linewidths in noble metals", "author": [ { "family_name": "Tang", "given_name": "Xiaoli", "clpid": "Tang-Xiaoli" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Phonon lifetimes in Cu, Ag, and Au at low and high temperatures were calculated along high symmetry directions using density functional theory combined with second-order perturbation theory. Both harmonic and third-order anharmonic force constants were computed using a supercell small displacement method, and the two-phonon densities of states were calculated for all three-phonon processes consistent with the kinematics of energy and momentum conservation. A nonrigorous Gr\u00fcneisen model with no q-dependence of the anharmonic coupling constants offers a simple separation of the potential and the kinematics, and proved semiquantitative for Cu, Ag, and Au. A rule is reported for finding the most anharmonic phonon mode in fcc metals.", "doi": "10.1103/PhysRevB.84.054303", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-08-09", "series_number": "5", "volume": "84", "issue": "5", "pages": "Art. No. 054303" }, { "id": "authors:1ye19-2hn59", "collection": "authors", "collection_id": "1ye19-2hn59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120530-104815505", "type": "article", "title": "Nonharmonic phonons in MgB_2 at elevated temperatures", "author": [ { "family_name": "Markovskiy", "given_name": "N. D.", "clpid": "Markovskiy-N-D" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was used to measure phonon spectra in MgB_2 and Mg_(0.75)Al_(0.25)B_2 from 7 to 750 K to investigate anharmonicity and adiabatic electron-phonon coupling. First-principles calculations of phonons with a linear response method were performed at multiple unit cell volumes, and the Helmholtz free energy was minimized to obtain the lattice parameters and phonon dynamics at elevated temperature in the quasiharmonic approximation. Most of the temperature dependence of the phonon density of states could be understood with the quasiharmonic approximation, although there was also significant thermal broadening of the phonon spectra. In comparison to Mg_(0.75)Al_(0.25)B_2, in the energy range of 60 to 80 meV the experimental phonon spectra from MgB_2 showed a nonmonotonic change with temperature around 500 K. This may originate from a change with temperature of the adiabatic electron-phonon coupling.", "doi": "10.1103/PhysRevB.83.174301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-05-04", "series_number": "17", "volume": "83", "issue": "17", "pages": "Art. No. 174301" }, { "id": "authors:sf50p-7jg74", "collection": "authors", "collection_id": "sf50p-7jg74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110505-113857907", "type": "article", "title": "Rapid Electron Dynamics at Fe Atoms in Nanocrystalline Li_(0.5)FePO_4 Studied by M\u00f6ssbauer Spectrometry", "author": [ { "family_name": "Tan", "given_name": "Hongjin", "clpid": "Tan-Hongjin" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Two-phase mixtures of Li_(0.5)FePO_4 with crystal sizes as small as 25 nm were prepared by solid-state reaction, ball milling, and chemical delithiation. Mssbauer spectra of nanocrystalline Li_(0.5)FePO_4 found evidence for a thin layer of Fe^(3+) at the crystal surfaces. Spectra acquired at temperatures from 25 to 225 \u00b0C showed thermally driven electronic relaxations, where the electric field gradients (EFG) of the main Fe^(3+) and Fe^(2+) spectral components decreased with temperature. The isomer shifts (IS) of Fe^(3+) and Fe^(2+) showed similar thermal trends, indicative of valence fluctuations caused by small polaron hopping. The activation energies obtained from the temperature dependence of the EFG were 410 meV for Fe^(3+) and 330 meV for Fe^(2+), and an activation energy of 400 meV was obtained for the IS of both. The rapid valence electron hopping between Fe sites is intrinsic to electronic conductivity in Li_(x)FePO_4, which is calculated to be higher than most reports for bulk material.", "doi": "10.1021/jp200127b", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2011-04-21", "series_number": "15", "volume": "115", "issue": "15", "pages": "7787-7792" }, { "id": "authors:11zwm-3ws67", "collection": "authors", "collection_id": "11zwm-3ws67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110912-102708891", "type": "article", "title": "Dynamics of iron atoms across the pressure-induced Invar transition in Pd_3Fe", "author": [ { "family_name": "Winterrose", "given_name": "M. L.", "clpid": "Winterrose-M-L" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Yue", "given_name": "A. F.", "clpid": "Yue-Alan-F" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Tan", "given_name": "Hongjin", "clpid": "Tan-Hongjin" }, { "family_name": "Xiao", "given_name": "Y.", "clpid": "Xiao-Yuming" }, { "family_name": "Chow", "given_name": "P.", "clpid": "Chow-Paul" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Toellner", "given_name": "T. S.", "clpid": "Toellner-T-S" }, { "family_name": "Alp", "given_name": "E. E.", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The ^(57)Fe phonon partial density of states (PDOS) in L1_2-ordered Pd_3Fe was studied at high pressures by nuclear resonant inelastic x-ray scattering (NRIXS) measurements and density functional theory (DFT) calculations. The NRIXS spectra showed that the stiffening of the ^(57)Fe PDOS with decreasing volume was slower from 12 to 24\u2002GPa owing to the pressure-induced Invar transition in Pd_3Fe, with a change from a high-moment ferromagnetic (FM) state to a low-moment (LM) state observed by nuclear forward scattering. Force constants obtained from fitting to a Born\u2013von K\u00e1rm\u00e1n model showed a relative softening of the first-nearest-neighbor (1NN) Fe-Pd longitudinal force constants at the magnetic transition. For the FM low-pressure state, the DFT calculations gave a PDOS and 1NN longitudinal force constants in good agreement with experiment, but discrepancies for the high-pressure LM state suggest the presence of short-range magnetic order.", "doi": "10.1103/PhysRevB.83.134304", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2011-04-20", "series_number": "13", "volume": "83", "issue": "13", "pages": "Art. No. 134304" }, { "id": "authors:2je33-tp204", "collection": "authors", "collection_id": "2je33-tp204", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110317-102805572", "type": "article", "title": "A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures", "author": [ { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "McKerns", "given_name": "Michael M.", "clpid": "McKerns-M-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Raman spectra of monoclinic zirconia (ZrO_2) were measured at temperatures of up to 950 K. Temperature-dependent Raman peak shifts\n and broadenings were reported and compared with prior results on hafnia\n (HfO_2). Lattice dynamics calculations were performed with both shell\n model and density functional theory to obtain Raman frequencies, and\n the total and partial phonon density of states. These calculations were\n also used to identify the individual motions of metal and oxygen atoms\n in the different Raman modes. By correlating these motions to the\n thermal peak shifts and broadenings, it was confirmed that modes\n involving changes in oxygen-oxygen bond length were the most\n anharmonic. The metal-dominated modes were found to be more\n quasiharmonic, and thus showed less broadening with temperature. Mass\n effects were evident by comparing the mode softening and shifting\n between zirconia and hafnia.", "doi": "10.1111/j.1551-2916.2010.04057.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2011-01", "series_number": "1", "volume": "94", "issue": "1", "pages": "125-130" }, { "id": "authors:fc0c0-k6773", "collection": "authors", "collection_id": "fc0c0-k6773", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110104-084939003", "type": "article", "title": "AtomSim: web-deployed atomistic dynamics simulator", "author": [ { "family_name": "Keith", "given_name": "J. Brandon", "clpid": "Keith-J-B" }, { "family_name": "Fennick", "given_name": "Jacob R.", "clpid": "Fennick-J-R" }, { "family_name": "Nelson", "given_name": "Daniel R.", "clpid": "Nelson-D-R" }, { "family_name": "Junkermeier", "given_name": "Chad E.", "clpid": "Junkermeier-C-E" }, { "family_name": "Lin", "given_name": "Jiao Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "McKerns", "given_name": "Michael M.", "clpid": "McKerns-M-M" }, { "family_name": "Lewis", "given_name": "James P.", "clpid": "Lewis-J-P" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "AtomSim, a collection of interfaces for computational crystallography simulations, has been developed. It uses forcefield-based dynamics through physics engines such as the General Utility Lattice Program, and can be integrated into larger computational frameworks such as the Virtual Neutron Facility for processing its dynamics into scattering functions, dynamical functions etc. It is also available as a Google App Engine-hosted web-deployed interface. Examples of a quartz molecular dynamics run and a hafnium dioxide phonon calculation are presented.", "doi": "10.1107/S0021889810037209", "issn": "0021-8898", "publisher": "International Union of Crystallography", "publication": "Journal of Applied Crystallography", "publication_date": "2010-12", "series_number": "6", "volume": "43", "issue": "6", "pages": "1553-1559" }, { "id": "authors:jw4dk-s0a88", "collection": "authors", "collection_id": "jw4dk-s0a88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101206-143055391", "type": "article", "title": "Anharmonicity-induced phonon broadening in aluminum at high temperatures", "author": [ { "family_name": "Tang", "given_name": "Xiaoli", "clpid": "Tang-Xiaoli" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Thermal phonon broadening in aluminum was studied by theoretical and experimental methods. Using\nsecond-order perturbation theory, phonon linewidths from the third-order anharmonicity were calculated from\nfirst-principles density-functional theory (DFT) with the supercell finite-displacement method. The importance\nof all three-phonon processes were assessed and individual phonon broadenings are presented. The good agreement between calculations and prior measurements of phonon linewidths at 300 K and new measurements of the phonon density of states to 750 K indicates that the third-order phonon-phonon interactions calculated from DFT can account for the lifetime broadenings of phonons in aluminum to at least 80% of its melting temperature.", "doi": "10.1103/PhysRevB.82.184301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2010-11-03", "series_number": "18", "volume": "82", "issue": "18", "pages": "Art. No. 184301" }, { "id": "authors:478x6-66p04", "collection": "authors", "collection_id": "478x6-66p04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101110-092304852", "type": "article", "title": "Effects of composition, temperature, and magnetism on phonons in bcc Fe-V alloys", "author": [ { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Markovskiy", "given_name": "N. D.", "clpid": "Markovskiy-N-D" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Keith", "given_name": "J. B.", "clpid": "Keith-J-B" }, { "family_name": "Winterrose", "given_name": "M. L.", "clpid": "Winterrose-M-L" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Lerche", "given_name": "M.", "clpid": "Lerche-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phonon densities of states of body-centered-cubic Fe-V alloys across the full composition range were studied by inelastic neutron scattering, nuclear resonant inelastic x-ray scattering, and ab initio calculations. The average phonon energy followed the inverse of the electronic heat capacity and the inverse of the electronic density of states at the Fermi level, showing how the interatomic forces depend on electronic screening. These quantities, including phonon energy, changed rapidly near the composition of the paramagnetic-ferromagnetic transition. For Fe- and V-rich alloys, the thermal phonon softening deviated from quasiharmonic behavior but better agreement was found for intermediate compositions. The Fe partial phonon density of states has a distinctly different shape than V for alloys with less than 50\u2002at.\u2009% Fe.", "doi": "10.1103/PhysRevB.82.144306", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2010-10-22", "series_number": "14", "volume": "82", "issue": "14", "pages": "Art. No. 144306" }, { "id": "authors:6g9jb-8r286", "collection": "authors", "collection_id": "6g9jb-8r286", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101026-093314517", "type": "article", "title": "Measurements of Hydrogen Spillover in Platinum Doped Superactivated Carbon", "author": [ { "family_name": "Stadie", "given_name": "Nicholas P.", "clpid": "Stadie-N-P" }, { "family_name": "Purewal", "given_name": "Justin J.", "clpid": "Purewal-J-J" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Hydrogen uptake was measured for platinum doped superactivated carbon at 296 K where hydrogen spillover was expected to occur. High pressure adsorption measurements using a Sieverts apparatus did not show an increase in gravimetric storage capacity over the unmodified superactivated carbon. Measurements of small samples (~0.2 g) over long equilibration times, consistent with the reported procedure, showed significant scatter and were not well above instrument background. In larger samples (~3 g), the hydrogen uptake was significantly above background but did not show enhancement due to spillover; total uptake scaled with the available surface area of the superactivated carbon. Any hydrogen spillover sorption was thus below the detection limit of standard volumetric gas adsorption measurements. Due to the additional mass of the catalyst nanoparticles and decreased surface area in the platinum doped system, the net effect of spillover sorption is detrimental for gravimetric density of hydrogen.", "doi": "10.1021/la9046758", "issn": "0743-7463", "publisher": "American Chemical Society", "publication": "Langmuir", "publication_date": "2010-10-05", "series_number": "19", "volume": "26", "issue": "19", "pages": "15481-15485" }, { "id": "authors:3j77g-yjg28", "collection": "authors", "collection_id": "3j77g-yjg28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100831-094242871", "type": "article", "title": "Effects of chemical composition and B2 order on phonons in bcc Fe\u2013Co alloys", "author": [ { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "Sheets", "given_name": "A. O.", "clpid": "Sheets-A-O" }, { "family_name": "Turgut", "given_name": "Z.", "clpid": "Turgut-Z" }, { "family_name": "Horwath", "given_name": "J.", "clpid": "Horwath-J" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Xiao", "given_name": "Yuming", "clpid": "Xiao-Yuming" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phonon density of states (DOS) gives insight into interatomic forces and provides the vibrational entropy, making it a key thermodynamic function for understanding alloy phase transformations. Nuclear resonant inelastic x-ray scattering and inelastic neutron scattering were used to measure the chemical dependence of the DOS of bcc Fe\u2013Co alloys. For the equiatomic alloy, the A2\u2192B2 (chemically disordered\u2192chemically ordered) phase transformation caused measurable changes in the phonon spectrum. The measured change in vibrational entropy upon ordering was \u22120.02\u00b10.02\u2002k_B/atom, suggesting that vibrational entropy results in a reduction in the order\u2013disorder transition temperature by 60\u00b160\u2002K. The Connolly\u2013Williams cluster inversion method was used to obtain interaction DOS (IDOS) curves that show how point and pair variables altered the phonon DOS of disordered bcc Fe\u2013Co alloys. These IDOS curves accurately captured the change in the phonon DOS and vibrational entropy of the B2 ordering transition.", "doi": "10.1063/1.3456500", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2010-07-15", "series_number": "2", "volume": "108", "issue": "2", "pages": "Art. No. 023519" }, { "id": "authors:kjccd-xqn98", "collection": "authors", "collection_id": "kjccd-xqn98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100303-145648322", "type": "article", "title": "Vibrational thermodynamics of materials", "author": [ { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The literature on vibrational thermodynamics of materials is reviewed. The emphasis is on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations. Some results on carbides, nitrides, oxides, hydrides and lithium-storage materials are also covered.\n\nPrinciples of harmonic phonons in alloys are organized into thermodynamic models for unmixing and ordering transformations on an Ising lattice, and extended for non-harmonic potentials. Owing to the high accuracy required for the phonon frequencies, quantitative predictions of vibrational entropy with analytical models prove elusive. Accurate tools for such calculations or measurements were challenging for many years, but are more accessible today. Ab initio methods for calculating phonons in solids are summarized. The experimental techniques of calorimetry, inelastic neutron scattering, and inelastic X-ray scattering are explained with enough detail to show the issues of using these methods for investigations of vibrational thermodynamics. The explanations extend to methods of data analysis that affect the accuracy of thermodynamic information.\n\nIt is sometimes possible to identify the structural and chemical origins of the differences in vibrational entropy of materials, and the number of these assessments is growing. There has been considerable progress in our understanding of the vibrational entropy of mixing in solid solutions, compound formation from pure elements, chemical unmixing of alloys, order\u2013disorder transformations, and martensitic transformations. Systematic trends are available for some of these phase transformations, although more examples are needed, and many results are less reliable at high temperatures. Nanostructures in materials can alter sufficiently the vibrational dynamics to affect thermodynamic stability. Internal stresses in polycrystals of anisotropic materials also contribute to the heat capacity. Lanthanides and actinides show a complex interplay of vibrational, electronic, and magnetic entropy, even at low temperatures.\n\nA \"quasiharmonic model\" is often used to extend the systematics of harmonic phonons to high temperatures by accounting for the effects of thermal expansion against a bulk modulus. Non-harmonic effects beyond the quasiharmonic approximation originate from the interactions of thermally-excited phonons with other phonons, or with the interactions of phonons with electronic excitations. In the classical high temperature limit, the adiabatic electron\u2013phonon coupling can have a surprisingly large effect in metals when temperature causes significant changes in the electron density near the Fermi level. There are useful similarities in how temperature, pressure, and composition alter the conduction electron screening and the interatomic force constants. Phonon\u2013phonon \"anharmonic\" interactions arise from those non-harmonic parts of the interatomic potential that cannot be accounted for by the quasiharmonic model. Anharmonic shifts in phonon frequency with temperature can be substantial, but trends are not well understood. Anharmonic phonon damping does show systematic trends, however, at least for fcc metals.\n\nTrends of vibrational entropy are often justified with atomic properties such as atomic size, electronegativity, electron-to-atom ratio, and mass. Since vibrational entropy originates at the level of electrons in solids, such rules of thumb prove no better than similar rules devised for trends in bonding and structure, and tend to be worse. Fortunately, the required tools for accurate experimental investigations of vibrational entropy have improved dramatically over the past few years, and the required ab initio methods have become more accessible. Steady progress is expected for understanding the phenomena reviewed here, as investigations are performed with the new tools of experiment and theory, sometimes in integrated ways.", "doi": "10.1016/j.pmatsci.2009.05.002", "issn": "0079-6425", "publisher": "Elsevier", "publication": "Progress in Materials Science", "publication_date": "2010-05", "series_number": "4", "volume": "55", "issue": "4", "pages": "247-352" }, { "id": "authors:xh8t8-e9c96", "collection": "authors", "collection_id": "xh8t8-e9c96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180914-101019530", "type": "article", "title": "A M\u00f6ssbauer Spectrometry Study of Electronic Processes in Li_xFePO_4", "author": [ { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-Hongjin" }, { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Li_xFePO_4 solid solutions with different lithium concentrations, x, were investigated by M\u00f6ssbauer spectrometry at temperatures between 25\u00b0 and 210\u00b0. The M\u00f6ssbauer spectra show a temperature dependence of their isomer shifts (E_(IS)) and electric quadrupole splittings (E_Q), typical of thermally-activated, electronic relaxation processes involving ^(57)Fe ions. The activation energies for the fluctuations of E_Q and E_(IS) do not have a measurable dependence on the concentration of lithium, but varies between Fe^(3+) and Fe^(2+). Typically, for the Fe^(2+) components of the spectra, the fluctuations of E_Q occurred at lower temperatures than the fluctuations of E_(IS), with activation energy of 512 meV for E_Q and 551 meV for E_(IS). The more facile fluctuations of E_Q for Fe^(2+) are evidence for local motions of neighboring Li^+ ions.", "doi": "10.1149/1.3265865", "issn": "1938-6737", "publisher": "Electrochemical Society", "publication": "ECS Transactions", "publication_date": "2009-12-18", "series_number": "27", "volume": "19", "issue": "27", "pages": "19-30" }, { "id": "authors:522hg-vb055", "collection": "authors", "collection_id": "522hg-vb055", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091208-135031033", "type": "article", "title": "Thermodynamic and Kinetic Stability of the Solid Solution Phase in Nanocrystalline Li_(x)FePO_4", "author": [ { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-H-J" }, { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Samples of nanostructured Li_(x)FePO_4 with characteristic crystal sizes of 26 nm, and compositions of x = 0.35 and 0.65, were synthesized by ball-milling and chemical delithiation. X-ray powder diffraction showed that the solid solution phase started to form whenever two-phase materials were heated above 200 \u00b0C. The solid solution phase of nanocrystalline Li_(0.65)FePO_4 was quick to form above 200 \u00b0C but did not unmix at lower temperatures. Unmixing below 200 \u00b0C was found after long-time annealing of nanocrystalline Li_(0.35)FePO_4, however, consistent with the equilibrium phase diagram of bulk Li_(x)FePO_4. The stability of the solid solution of nanocrystalline Li_(x)FePO_4 is kinetic in origin, perhaps originating with effects of crystal surfaces.", "doi": "10.1021/jp907161z", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2009-12-03", "series_number": "48", "volume": "113", "issue": "48", "pages": "20527-20530" }, { "id": "authors:ytakm-34z95", "collection": "authors", "collection_id": "ytakm-34z95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100121-085710926", "type": "article", "title": "Effects of vacancies on phonon entropy of B2 FeAl", "author": [ { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Winterrose", "given_name": "M. L.", "clpid": "Winterrose-M-L" }, { "family_name": "Swan-Wood", "given_name": "T.", "clpid": "Swan-Wood-T-L" }, { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M-G" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Hu", "given_name": "Jingzhu", "clpid": "Hu-Jingzhu" }, { "family_name": "Lerche", "given_name": "M.", "clpid": "Lerche-M" }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169", "clpid": "Hu-Michael-Y" }, { "family_name": "Somayazulu", "given_name": "M.", "clpid": "Somayazulu-M-S" } ], "abstract": "The phonon density of states (DOS) and phonon entropy of B2 FeAl were determined as functions of the Fe site vacancy concentration using several scattering techniques and were computed from first principles. Measurements at elevated temperature and pressure were performed to explore volume effects, test the usefulness of the quasiharmonic (QH) approximation, and provide comparison for the first-principles calculations. The average temperature and pressure dependencies of phonons were consistent with the QH model. The decrease in specific volume associated with the introduction of vacancies causes a stiffening of the DOS that was captured well with the experimentally determined Gr\u00fcneisen parameter. Features associated with vacancies in the DOS are not well explained by this model, however, especially in the gap between the acoustic and optic branches. First-principles calculations indicated that these modes are primarily associated with vibrations of Al atoms in the first-nearest-neighbor shell of the vacancy, with some vibration amplitude also involving the second-nearest-neighbor Fe atoms. At the vacancy concentrations of study, the phonon entropy of vacancy formation was found to be approximately \u22121.7k_B/atom, about half as large and of opposite sign as the configurational entropy of vacancy formation.", "doi": "10.1103/PhysRevB.80.214303", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2009-12", "series_number": "21", "volume": "80", "issue": "21", "pages": "Art. No. 214303" }, { "id": "authors:za8c8-5h572", "collection": "authors", "collection_id": "za8c8-5h572", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090923-143134720", "type": "article", "title": "Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures", "author": [ { "family_name": "Li", "given_name": "Chen W.", "orcid": "0000-0002-0758-5334", "clpid": "Li-Chen-W" }, { "family_name": "McKerns", "given_name": "Michael M.", "clpid": "McKerns-M-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Raman spectra of monoclinic hafnium oxide (HfO_2) were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and broadenings, it was found that modes involving changes in oxygen-oxygen bond length were the most anharmonic. The hafnium-dominated modes were more quasiharmonic and showed less broadening with temperature. Comparatively, the oxygen-dominated modes were more influenced by the cubic term in the interatomic potential than the hafnium-dominated modes. An approximately quadratic correlation was found between phonon-line broadening and softening.", "doi": "10.1103/PhysRevB.80.054304", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2009-08-01", "series_number": "5", "volume": "80", "issue": "5", "pages": "Art. No. 054304" }, { "id": "authors:3sxmr-vd291", "collection": "authors", "collection_id": "3sxmr-vd291", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090901-084412556", "type": "article", "title": "Pressure-Induced Invar Behavior in Pd_3Fe", "author": [ { "family_name": "Winterrose", "given_name": "M. L.", "clpid": "Winterrose-M-L" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Yue", "given_name": "A. F.", "clpid": "Yue-A-F" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Mauger", "given_name": "L.", "clpid": "Mauger-L" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Hu", "given_name": "Jingzhu", "clpid": "Hu-Jingzhu" }, { "family_name": "Lerche", "given_name": "M.", "clpid": "Lerche-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Synchrotron x-ray diffraction (XRD) measurements, nuclear forward scattering (NFS) measurements, and density functional theory (DFT) calculations were performed on L1_2-ordered Pd_3Fe. Measurements were performed at 300 K at pressures up to 33 GPa, and at 7 GPa at temperatures up to 650 K. The NFS revealed a collapse of the ^(57)Fe magnetic moment between 8.9 and 12.3 GPa at 300 K, coinciding with a transition in bulk modulus found by XRD. Heating the sample under a pressure of 7 GPa showed negligible thermal expansion from 300 to 523 K, demonstrating Invar behavior. Zero-temperature DFT calculations identified a ferromagnetic ground state and showed several antiferromagnetic states had comparable energies at pressures above 20 GPa.", "doi": "10.1103/PhysRevLett.102.237202", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2009-06-12", "series_number": "23", "volume": "102", "issue": "23", "pages": "Art. No. 237202" }, { "id": "authors:fmnpp-0am63", "collection": "authors", "collection_id": "fmnpp-0am63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090727-112832709", "type": "article", "title": "Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers", "author": [ { "family_name": "Purewal", "given_name": "J. J.", "clpid": "Purewal-J-J" }, { "family_name": "Kabbour", "given_name": "H.", "clpid": "Kabbour-H" }, { "family_name": "Vajo", "given_name": "J. J.", "orcid": "0000-0002-6271-4899", "clpid": "Vajo-J-J" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Pore size distributions (PSD) and supercritical H_2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H_2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H_2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference.", "doi": "10.1088/0957-4484/20/20/204012", "issn": "0957-4484", "publisher": "IOP", "publication": "Nanotechnology", "publication_date": "2009-05-20", "series_number": "20", "volume": "20", "issue": "20", "pages": "204012" }, { "id": "authors:gc3hy-2cs92", "collection": "authors", "collection_id": "gc3hy-2cs92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090902-083907646", "type": "article", "title": "M\u00f6ssbauer Spectrometry Study of Thermally-Activated Electronic Processes in Li_xFePO_4", "author": [ { "family_name": "Tan", "given_name": "H. J.", "clpid": "Tan-H-J" }, { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The solid solution phase of Li_xFePO_4 with different Li concentrations, x, was investigated by M\u00f6ssbauer spectrometry at temperatures between 25 and 210 \u00b0C. The M\u00f6ssbauer spectra show a temperature dependence of their isomer shifts (E_(IS)) and electric quadrupole splittings (E_Q), typical of thermally activated, electronic relaxation processes involving ^(57)Fe ions. The activation energies for the fluctuations of E_Q and E_(IS) for Fe^(3+) are nearly the same, 570 \u00b1 9 meV, suggesting that both originate from charge hopping. For the Fe^(2+) components of the spectra, the fluctuations of E_Q occurred at lower temperatures than the fluctuations of E_(IS), with an activation energy of 512 \u00b1 12 meV for E_Q and one of 551 \u00b1 7 meV for E_(IS). The more facile fluctuations of E_Q for Fe^(2+) are evidence for local motions of neighboring Li^+ ions. It appears that the electron hopping frequency is lower than that of Li^+ ions. The activation energies of relaxation did not have a measurable dependence on the concentration of lithium, x.", "doi": "10.1021/jp808537z", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2009-02-12", "series_number": "6", "volume": "113", "issue": "6", "pages": "2526-2531" }, { "id": "authors:mmwsx-3fj22", "collection": "authors", "collection_id": "mmwsx-3fj22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090831-151955826", "type": "article", "title": "Adsorption and melting of hydrogen in potassium-intercalated graphite", "author": [ { "family_name": "Purewal", "given_name": "J. J.", "clpid": "Purewal-J-J" }, { "family_name": "Keith", "given_name": "J. B.", "clpid": "Keith-J-B" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Brown", "given_name": "C. M.", "clpid": "Brown-C-M" }, { "family_name": "Tyagi", "given_name": "M.", "clpid": "Tiyagi-M" } ], "abstract": "Volumetric adsorption and quasielastic neutron scattering are used to study the diffusion and thermodynamics of sorbed H_2 in the graphite intercalation compound KC24. A sorption enthalpy of 8.5 kJ/mol at zero coverage is determined from H_2 adsorption isotherms. From measurements of total elastic-neutron-scattering intensity as a function of temperature, a melting transition of the H_2 adsorbate is observed at 35 K for KC_(24)(H_2)_1. Quasielastic-neutron-scattering (QENS) spectra reveal distinct slow- and fast-H_2-diffusion processes which exist simultaneously at temperatures above the transition point. The temperature dependence of the characteristic diffusion times follows an Arrhenius relation tau=tau_0 exp(E_a/T), where tau_0^(fast)=1.0\u00b10.1 ps, tau_0^(slow)=21\u00b12 ps, E_a^(fast)=156\u00b15 K, and E_a^(slow)=189\u00b15 K. The fast-diffusion process is attributable to individual motions of H_2 molecules in a static potassium structure, and the slow-diffusion process could be attributable to fluctuations in H_2 particle density correlated with jumps of potassium atoms. The QENS spectra at low Q are used to discuss the dimensionality of the diffusion process.", "doi": "10.1103/PhysRevB.79.054305", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2009-02-01", "series_number": "5", "volume": "79", "issue": "5", "pages": "Art. No. 054305" }, { "id": "authors:s8arf-khd88", "collection": "authors", "collection_id": "s8arf-khd88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CHRIprl08", "type": "article", "title": "Phonon Density of States of LaFeAsO_(1-x)F_x", "author": [ { "family_name": "Christianson", "given_name": "A. D.", "clpid": "Christianson-A-D" }, { "family_name": "Lumsden", "given_name": "M. D.", "clpid": "Lumsden-M-D" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Stone", "given_name": "M. B.", "orcid": "0000-0001-7884-9715", "clpid": "Stone-M-B" }, { "family_name": "Abernathy", "given_name": "D. L.", "orcid": "0000-0002-3533-003X", "clpid": "Abernathy-Douglas-L" }, { "family_name": "McGuire", "given_name": "M. A.", "clpid": "McGuide-M-A" }, { "family_name": "Sefat", "given_name": "A. S.", "clpid": "Sefat-A-S" }, { "family_name": "Jin", "given_name": "R.", "clpid": "Jin-R" }, { "family_name": "Sales", "given_name": "B. C.", "clpid": "Sales-B-C" }, { "family_name": "Mandrus", "given_name": "D.", "orcid": "0000-0003-3616-7104", "clpid": "Mandrus-D" }, { "family_name": "Mun", "given_name": "E. D.", "clpid": "Mun-E-D" }, { "family_name": "Canfield", "given_name": "P. C.", "clpid": "Canfield-P-C" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Lucas", "given_name": "M.", "clpid": "Lucas-M-S" }, { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Keith", "given_name": "J. B.", "clpid": "Keith-J-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Goremychkin", "given_name": "E. A.", "clpid": "Goremychkin-E-A" }, { "family_name": "McQueeney", "given_name": "R. J.", "clpid": "McQueeney-R-J" } ], "abstract": "We have studied the phonon density of states (PDOS) in LaFeAsO1-xFx with inelastic neutron scattering methods. The PDOS of the parent compound (x=0) is very similar to the PDOS of samples optimally doped with fluorine to achieve the maximum Tc (x~0.1). Good agreement is found between the experimental PDOS and first-principles calculations with the exception of a small difference in Fe mode frequencies. The PDOS reported here is not consistent with conventional electron-phonon mediated superconductivity.", "doi": "10.1103/PhysRevLett.101.157004", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2008-10-10", "series_number": "15", "volume": "101", "issue": "15", "pages": "Art. No. 157004" }, { "id": "authors:brg2f-bzg66", "collection": "authors", "collection_id": "brg2f-bzg66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DELprl08", "type": "article", "title": "Adiabatic Electron-Phonon Interaction and High-Temperature Thermodynamics of A15 Compounds", "author": [ { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was used to measure the phonon densities of states of the A15 compounds V_3Si, V_3Ge, and V_3Co at temperatures from 10 to 1273 K. It was found that phonons in V_3Si and V_3Ge, which are superconducting at low temperatures, exhibit an anomalous stiffening with increasing temperature, whereas phonons in V_3Co have a normal softening behavior. First-principles calculations show that this anomalous increase in phonon frequencies at high temperatures originates with an adiabatic electron-phonon coupling mechanism. The anomaly is caused by the thermally induced broadening of sharp peaks in the electronic density of states of V_3Si and V_3Ge, which tends to decrease the electronic density at the Fermi level. These results show that the adiabatic electron-phonon coupling can influence the phonon thermodynamics at temperatures exceeding 1000 K.", "doi": "10.1103/PhysRevLett.101.105504", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2008-09-05", "series_number": "10", "volume": "101", "issue": "10", "pages": "Art. No. 105504" }, { "id": "authors:dntm4-c9211", "collection": "authors", "collection_id": "dntm4-c9211", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170426-140106425", "type": "article", "title": "Hydrogen Sorption Behavior of the ScH_2\u2212LiBH_4 System: Experimental Assesment of Chemical Destabilization Effects", "author": [ { "family_name": "Purewal", "given_name": "Justin", "clpid": "Purewal-J-J" }, { "family_name": "Hwang", "given_name": "Son-Jong", "orcid": "0000-0002-3210-466X", "clpid": "Hwang-Son-Jong" }, { "family_name": "Bowman", "given_name": "Robert C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "R\u00f6nnebro", "given_name": "Ewa", "clpid": "R\u00f6nnebro-E" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ahn", "given_name": "Channing", "clpid": "Ahn-C-C" } ], "abstract": "The hydrogen storage reaction ScH_2 + 2LiBH_4 \u2192 ScB_2 + 2LiH + 4H_2 (8.91 wt %), based on the thermodynamic destabilization of LiBH_4, is predicted to have a reaction enthalpy of \u0394H_(300K) = 34.1 kJ/mol H_2. The isothermal kinetic desorption behavior in this system was measured. At temperatures up to 450 \u00b0C, less than 5 wt % H_2 is released, which is only half of the theoretical capacity. Powder X-ray diffraction data indicate that LiBH_4 has decomposed into LiH in the final desorption product, but the data provide no evidence that ScH_2 has participated in the reaction. Magic angle spinning NMR (MAS NMR) results do not show that the expected ScB_2 equilibrium product phase has formed during desorption. While the addition of 2 mol % TiCl_3 catalyst does improve desorption kinetics at 280 \u00b0C, it does not otherwise assist the destabilization reaction. The calculated reaction enthalpy suggests that this system should be of interest at moderate temperatures, but the large heats of formation of the reactant phases in this system appear to play a critical role in determining overall kinetics. Furthermore, the formation of a Li_2B_(12)H_(12) intermediate phase was determined by MAS NMR, which is an undesirable stable product if reaction reversibility is to be accomplished.", "doi": "10.1021/jp800486n", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2008-06-05", "series_number": "22", "volume": "112", "issue": "22", "pages": "8481-8485" }, { "id": "authors:enp8a-kn705", "collection": "authors", "collection_id": "enp8a-kn705", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DELprb08", "type": "article", "title": "Electron-phonon interactions and high-temperature thermodynamics of vanadium and its alloys", "author": [ { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Mu\u00f1oz", "given_name": "J. A.", "clpid": "Mu\u00f1oz-J-A" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering was used to measure the phonon densities of states (DOSs) for pure V and solid solutions of V with 6 to 7at% of Co, Nb, and Pt, at temperatures from 10 K to 1323 K. Ancillary measurements of heat capacity and thermal expansion are reported on V and V-7at%Co and used to help identify the different sources of entropy. Pure V exhibits an anomalous anharmonic stiffening of phonons with increasing temperature. This anharmonicity is suppressed by Co and Pt, but not by isoelectronic Nb solutes. The changes in phonon frequency with alloying and with temperature both correlate to the decrease in electron density of states (DOS) at the Fermi level as calculated using density functional theory. The effects of both temperature and alloying can be understood in terms of an adiabatic electron-phonon interaction (EPI), which broadens sharp features in the electron DOS. These results show that the adiabatic EPI can influence the phonon thermodynamics at temperatures exceeding 1000 K, and that thermal trends of phonons may help assess the strength of the EPI.", "doi": "10.1103/PhysRevB.77.214112", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2008-06-01", "series_number": "21", "volume": "77", "issue": "21", "pages": "Art. No. 214112" }, { "id": "authors:k2fee-z0r04", "collection": "authors", "collection_id": "k2fee-z0r04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KEIjpcm08", "type": "article", "title": "Ab initio free energy of vacancy formation and mass-action kinetics in vis-active TiO2", "author": [ { "family_name": "Keith", "given_name": "J. Brandon", "clpid": "Keith-J-B" }, { "family_name": "Wang", "given_name": "Hao", "clpid": "Wang-Hao" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Lewis", "given_name": "James P.", "clpid": "Lewis-J-P" } ], "abstract": "Recent reports have identified bulk defects such as oxygen vacancies as key players in visible-light photoactive TiO2. This would imply greater visible light absorption rates may be possible provided effective defect engineering can be achieved. To further this we have developed methods to simulate vacancy formation in bulk TiO2 using ab initio techniques. Initial results of these methods show an entropic reduction in the free energy of vacancy formation of 2.3 eV over a range of 266 K. The use of this result is illustrated by a 'toy' mass-action kinetics model which offers insight into vacancy concentration, rate constants, and enthalpy of reaction.", "doi": "10.1088/0953-8984/20/02/022202", "issn": "0953-8984", "publisher": "IOP", "publication": "Journal of Physics: Condensed Matter", "publication_date": "2008-01-16", "series_number": "2", "volume": "20", "issue": "2", "pages": "Art. No. 022202" }, { "id": "authors:6hf6m-31e21", "collection": "authors", "collection_id": "6hf6m-31e21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KREprb08", "type": "article", "title": "Phonons in aluminum at high temperatures studied by inelastic neutron scattering", "author": [ { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Lucas", "given_name": "M.", "clpid": "Lucas-M-S" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering measurements on aluminum metal were performed at temperatures of 10, 150, 300, 525, and 775 K using direct-geometry Fermi chopper spectrometers. The temperature dependent phonon density of states (DOS) was determined from the scattering, and was used to fit Born\u2013von K\u00e1rm\u00e1n models of lattice dynamics. The shifts in the phonon frequencies with increasing temperature were largely explained by the softening of the longitudinal force constants out to third nearest neighbors. A significant broadening of the phonon spectra at high temperatures was also measured. The phonon DOS was used to determine the vibrational contributions to the entropy of aluminum as a function of temperature. All other contributions to the entropy of aluminum were calculated or assessed, and the total entropy was in excellent agreement with the NIST-JANAF compilation [M. W. Chase, J. Phys. Chem. Ref. Data Monogr. 9, 59 (1998)]. Anharmonic effects were attributed to phonon-phonon interactions. The quasiharmonic approximation was generally successful, but its weaknesses are discussed.", "doi": "10.1103/PhysRevB.77.024301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2008-01-01", "series_number": "2", "volume": "77", "issue": "2", "pages": "Art. No. 024301" }, { "id": "authors:kkv5r-xt196", "collection": "authors", "collection_id": "kkv5r-xt196", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170609-082013038", "type": "article", "title": "Local Electronic Structure of Olivine Phases of Li_xFePO_4", "author": [ { "family_name": "Miao", "given_name": "Shu", "clpid": "Miao-Shu" }, { "family_name": "Kocher", "given_name": "Michael", "clpid": "Kocher-M" }, { "family_name": "Rez", "given_name": "Peter", "clpid": "Rez-P" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" } ], "abstract": "Changes in the local electronic structure at atoms around Li sites in the olivine phase of LiFePO4 were studied during delithiation. Electron energy loss spectrometry was used for measuring shifts and intensities of the near-edge structure at the K-edge of O and at the L-edges of P and Fe. Electronic structure calculations were performed on these materials with a plane-wave pseudopotential code and with an atomic multiplet code with crystal fields. It is found that both Fe and O atoms accommodate some of the charge around the Li+ ion, evidently in a hybridized Fe\u2212O state. The O 2p levels appear to be fully occupied at the composition LiFePO_4. With delithiation, however, these states are partially emptied, suggestive of a more covalent bonding to the oxygen atom in FePO_4 as compared to LiFePO_4. The same behavior is found for the white lines at the Fe L_(2,3)-edges, which also undergo a shift in energy upon delithiation. A charge transfer of up to 0.48 electrons is found at the Fe atoms, as determined from white line intensity variations after delithiation, while the remaining charge is compensated by O atoms. No changes are evident at the P L_(2,3)-edges.", "doi": "10.1021/jp068605q", "issn": "1089-5639", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry A", "publication_date": "2007-05-24", "series_number": "20", "volume": "111", "issue": "20", "pages": "4242-4247" }, { "id": "authors:ega50-55178", "collection": "authors", "collection_id": "ega50-55178", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101007-115811939", "type": "article", "title": "XRD evidence of macroscopic composition inhomogeneities in the graphite\u2013lithium electrode", "author": [ { "family_name": "Reynier", "given_name": "Yvan", "clpid": "Reynier-Y" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "In situ and ex situ X-ray diffraction (XRD) measurements were carried out on lithiated graphite electrodes at different states of charge. Data were collected from both sides of electrode. We found macroscopic inhomogeneities in the lithium concentration along the electrode thickness even when the electrode was allowed to rest for 24 h. The electrode side facing the lithium counter electrode in the coin type half-cell displays higher lithium concentration as compared to the side opposed to the XRD window. Residual stage 2 compound is found in the supposedly fully lithiated and fully delithiated electrode. It seems that the differences in the chemical potential between stage 2 and stage 1 is too small to average the lithium composition through chemical diffusion at ambient temperature in reasonable times.", "doi": "10.1016/j.jpowsour.2006.10.023", "issn": "0378-7753", "publisher": "Elsevier", "publication": "Journal of Power Sources", "publication_date": "2007-03-20", "series_number": "2", "volume": "165", "issue": "2", "pages": "616-619" }, { "id": "authors:kvvvg-e0s32", "collection": "authors", "collection_id": "kvvvg-e0s32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101007-102744850", "type": "article", "title": "Evolution of lithiation thermodynamics with the graphitization of carbons", "author": [ { "family_name": "Reynier", "given_name": "Y.", "clpid": "Reynier-Y" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Barsukov", "given_name": "I.", "clpid": "Barsukov-I" } ], "abstract": "Instrumentation was developed to study the thermodynamics of lithium intercalation in cokes that were heat-treated at different temperatures. The method measures the open circuit voltages of electrochemical cells as a function of temperature, and obtains the entropy and enthalpy of the lithiation reaction. X-ray diffractometry and Raman spectroscopy were used to determine the structure of the carbon materials after heat treatment. The effect of the degree of graphitization on the entropy and enthalpy of lithium intercalation was thereby determined. A model is proposed to correlate the degree of graphitization to entropy profiles. It is shown that graphs of entropy versus open circuit voltage for different states of charge give quantitative information on graphitization, making them useful for the structural characterization of partially-graphitized carbons.", "doi": "10.1016/j.jpowsour.2006.10.024", "issn": "0378-7753", "publisher": "Elsevier", "publication": "Journal of Power Sources", "publication_date": "2007-03-20", "series_number": "2", "volume": "165", "issue": "2", "pages": "552-558" }, { "id": "authors:acfg5-ce971", "collection": "authors", "collection_id": "acfg5-ce971", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PRYprb07", "type": "article", "title": "Transition metal d-band occupancy in skutterudites studied by electron energy-loss spectroscopy", "author": [ { "family_name": "Prytz", "given_name": "\u00d8", "clpid": "Prytz-\u00d8" }, { "family_name": "Taft\u00f8", "given_name": "J.", "clpid": "Taft\u00f8-J" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The transition-metal 3d occupancy of a series of thermoelectric skutterudites is investigated using electron energy-loss spectroscopy. We find that bonding causes an emptying of the 3d states in the binary skutterudites CoP3, CoAs3, CoSb3, and NiP3, while compared to the pure Fe the 3d occupancy in LaFe4P12 is significantly increased, consistent with the idea that each interstitial La atom (rattler) donates three electrons to compensate for missing valence electron of Fe as compared to Co. These experimental results are in agreement with previous models suggesting a predominantly covalent bonding between transition metal and pnictogen atoms in skutterudites, and provide evidence of charge transfer from La to the Fe-P complex in LaFe4P12.", "doi": "10.1103/PhysRevB.75.125109", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2007-03-15", "series_number": "12", "volume": "75", "issue": "12", "pages": "Art. No. 125109" }, { "id": "authors:tkagx-kcw76", "collection": "authors", "collection_id": "tkagx-kcw76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KREprb07", "type": "article", "title": "Neutron scattering measurements of phonons in nickel at elevated temperatures", "author": [ { "family_name": "Kresch", "given_name": "M.", "clpid": "Kresch-M" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Stevens", "given_name": "R.", "clpid": "Stevens-R" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Measurements of elastic and inelastic neutron scatterings from elemental nickel were made at 10, 300, 575, 875, and 1275 K. The phonon densities of states (DOSs) were calculated from the inelastic scattering and were fit with Born\u2013von K\u00e1rm\u00e1n models of the lattice dynamics. With ancillary data on thermal expansion and elastic moduli, we found a small, negative anharmonic contribution to the phonon entropy at high temperature. We used this to place bounds on the magnetic entropy of nickel. A significant broadening of the phonon DOS at elevated temperatures, another indication of anharmonicity, was also measured and quantified.", "doi": "10.1103/PhysRevB.75.104301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2007-03-01", "series_number": "10", "volume": "75", "issue": "10", "pages": "Art. No. 104301" }, { "id": "authors:zq86v-38z59", "collection": "authors", "collection_id": "zq86v-38z59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LUCprb07", "type": "article", "title": "Partial phonon densities of states of 57Fe in Fe-Cr: Analysis by a local-order cluster expansion", "author": [ { "family_name": "Lucas", "given_name": "Matthew S.", "clpid": "Lucas-M-S" }, { "family_name": "Papandrew", "given_name": "A.", "clpid": "Papandrew-A-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Hu", "given_name": "Michael Y.", "orcid": "0000-0002-3718-7169", "clpid": "Hu-Michael-Y" } ], "abstract": "Nuclear resonant inelastic x-ray scattering spectra were measured for 57Fe in disordered body-centered-cubic alloys of Fe-Cr. Partial phonon density of states (DOS) curves were obtained from these data. These results, in conjunction with the results of Ruckert et al. [Hyperfine Interact. 126, 363 (2000)] on Fe-Cr thin-film multilayers and alloys, were analyzed with a local-order cluster expansion method. Interaction partial phonon DOS functions for the different short-range correlation functions were obtained from the disordered alloys. These interaction DOS functions were used in reconstructing the 57Fe partial DOS curves measured by Ruckert et al. on a set of thin-film multilayer samples of 57Fe/56Fe/Cr. The method worked well using terms up to a combined first- and second-nearest-neighbor triangle cluster, which were obtained reliably from the disordered alloys. The limitations of a basis set of correlation functions from disordered alloys are discussed but shown to be acceptable for the chemical trends of phonons in the Fe-Cr system.", "doi": "10.1103/PhysRevB.75.054307", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2007-02-01", "series_number": "5", "volume": "75", "issue": "5", "pages": "Art. No. 054307" }, { "id": "authors:4vhms-95f61", "collection": "authors", "collection_id": "4vhms-95f61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170609-091425287", "type": "article", "title": "Valence Fluctuations of ^(57)Fe in Disordered Li_(0.6)FePO_4", "author": [ { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The local electronic structure around iron ions in Li_(0.6)FePO)4 was studied by ^(57)Fe M\u00f6ssbauer spectrometry at temperatures from 25 to 240 \u00b0C. The equilibrium two-phase, triphylite plus heterosite, material was compared to a disordered solid solution that was obtained by quenching from a high temperature. Substantial electronic relaxations were found in the disordered solid solution compared to the two-phase material at temperatures of 130 \u00b0C and above. Fluctuations in the electric field gradient showed an approximately Arrhenius behavior, with an activation energy of 335 \u00b1 25meV and a prefactor of 5 \u00d7 10^(11) Hz, whereas Arrhenius plots for the isomer shift showed activation energies of approximately 600 meV. It is suggested that these spectral relaxations are caused by the motions of Li^+ ions. A slight relaxation at 180 \u00b0C in 10% of the two-phase material can be attributed to defects in the heterosite and triphylite phases. Overall, the disordered solid solution phase shows faster electronic dynamics than the two-phase material.", "doi": "10.1021/jp067710x", "issn": "1932-7447", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry C", "publication_date": "2007-02-01", "series_number": "4", "volume": "111", "issue": "4", "pages": "1563-1566" }, { "id": "authors:ayfy4-vsv69", "collection": "authors", "collection_id": "ayfy4-vsv69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DELprl06", "type": "article", "title": "Charge Redistribution and Phonon Entropy of Vanadium Alloys", "author": [ { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The effects of alloying on the lattice dynamics of vanadium were investigated using inelastic neutron scattering. Phonon densities of states were obtained for bcc solid solutions of V with 3d, 4d, and 5d transition metal solutes, from which vibrational entropies of alloying were obtained. A good correlation is found between the vibrational entropy of alloying and the electronegativity of transition metal solutes across the 3d row and down columns of the periodic table. First-principles calculations on supercells matching the experimental compositions predicted a systematic charge redistribution in the nearest-neighbor shell around the solute atoms, also following the Pauling and Watson electronegativity scales. The systematic stiffening of the phonons is interpreted in terms of the modified screening properties of the electron density around the solutes.", "doi": "10.1103/PhysRevLett.97.245701", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2006-12-15", "series_number": "24", "volume": "97", "issue": "24", "pages": "Art. No. 245701" }, { "id": "authors:nbt12-rma27", "collection": "authors", "collection_id": "nbt12-rma27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180913-133203597", "type": "article", "title": "The electronic properties of chemically delithiated Li_xFePO_4", "author": [ { "family_name": "Dodd", "given_name": "J.", "clpid": "Dodd-J-L" }, { "family_name": "Ait Salah", "given_name": "A.", "clpid": "Ait-Salah-A" }, { "family_name": "Mauger", "given_name": "A.", "clpid": "Mauger-A" }, { "family_name": "Gendron", "given_name": "F.", "clpid": "Gendron-F" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Julien", "given_name": "C. M.", "clpid": "Julien-C-M" } ], "abstract": "We report on the structure and the electronic features of LiFePO4 and the delithiated mixture (1-x)Li_1FePO_4 + x Li_0FePO_4 powder obtained by chemical delithiation. X-ray diffraction, Fourier transform infrared spectroscopy, and magnetic experiments are analyzed for x = 0.0, 0.5, and 1.0. The magnetic properties give evidence of a super-paramagnetism associated to iron-based ferromagnetic nanoparticles, superposed to the intrinsic magnetic contribution of LiFePO_4 which undergoes an antiferromagnetic ordering at T_N(x=1)=50 K and T_N(x=0)=125 K. Magnetization curves show superparamagnetism due to nanometer- sized magnetic particles. The magnetic clustering (amount of iron in the ferromagnetic nanoparticles, mean size distribution) is independent of the lithium concentration.", "doi": "10.1149/1.2209355", "issn": "1938-6737", "publisher": "Electrochemical Society", "publication": "ECS Transactions", "publication_date": "2006-11-28", "series_number": "26", "volume": "1", "issue": "26", "pages": "39-45" }, { "id": "authors:9erbx-3pg09", "collection": "authors", "collection_id": "9erbx-3pg09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180913-133203503", "type": "article", "title": "Determining the Phase Diagram of Li_xFePO_4", "author": [ { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phase diagram for Li_xFePO_4 has been determined for different lithium concentrations and temperatures. X-ray diffraction analysis was used to determine phase fractions at temperatures between room temperature and 400 \u00b0C for Li_xFePO_4 at different states of lithiation. The two low- temperature phases, heterosite and triphylite, have previously been shown to transform to a disordered solid solution at elevated temperatures. This disordered phase allows for a continuous transition between the heterosite and triphylite phases and is stable at relatively low temperatures. At intermediate temperatures the proposed phase diagram resembles a eutectoid system, with eutectoid point at around x=0.6 and 200 \u00b0C. Kinetics of mixing and unmixing transformations are reported, including the hysteresis between heating and cooling. The enthalpy of this transition is at least 700 J/mol.", "doi": "10.1149/1.2209354", "issn": "1938-6737", "publisher": "Electrochemical Society", "publication": "ECS Transactions", "publication_date": "2006-11-28", "series_number": "26", "volume": "1", "issue": "26", "pages": "27-38" }, { "id": "authors:nm9ed-zm618", "collection": "authors", "collection_id": "nm9ed-zm618", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180913-133203686", "type": "article", "title": "Entropymetry of Lithium Intercalation in Spinel Manganese Oxide: Effect of Lithium Stoichiometry", "author": [ { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Reynier", "given_name": "Y.", "clpid": "Reynier-Y" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Cathodes based on cubic (spinel) structure LiMn_2O_4 were investigated by electrochemical entropymetry in an attempt to characterize their phase diagram according to the initial lithium composition. The stoichiometric material shows a very pronounced 2-phase region in the high 4V plateau and a solid- solution behavior in the lower 4V plateau. A third region is found in the non stoichiometric material characterized by a steep increase in entropy. This may relate to the onset of a stoichiometry induced anticipated cubic to tetragonal phase transition in the 4V area in this material. The later has been so far reported to occur only in the 3V area.", "doi": "10.1149/1.2209361", "issn": "1938-6737", "publisher": "Electrochemical Society", "publication": "ECS Transactions", "publication_date": "2006-11-28", "series_number": "26", "volume": "1", "issue": "26", "pages": "87-96" }, { "id": "authors:6bvhn-edm16", "collection": "authors", "collection_id": "6bvhn-edm16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170419-100955822", "type": "article", "title": "Phonons and Thermodynamics of Unmixed and Disordered Li_(0.6)FePO_4", "author": [ { "family_name": "Stevens", "given_name": "R.", "clpid": "Stevens-R" }, { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Kresch", "given_name": "M. G.", "clpid": "Kresch-M-G" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ellis", "given_name": "B.", "clpid": "Ellis-B" }, { "family_name": "Nazar", "given_name": "L. F.", "clpid": "Nazar-L-F" } ], "abstract": "The lithium-storage material Li_(0.6)FePO_4 was studied by inelastic neutron scattering and differential scanning calorimetry. Li_(0.6)FePO_4 undergoes a transformation from a two-phase mixture (heterosite and triphylite) to a disordered solid-solution at 200 \u00b0C. Phonon densities of states (DOS) obtained from the inelastic neutron scattering were similar for the two-phase sample measured at 180 \u00b0C and the disordered sample measured at 220 \u00b0C. The vibrational entropy of transformation is 1.8 \u00b10.9 J/(K mol), which is smaller than the configurational entropy difference of approximately 3.1 J/(K mol). The measured enthalpy of the disordering transition was estimated as 2.5 kJ/mol. The phonon data show a small change in lattice dynamics upon disordering.", "doi": "10.1021/jp063831l", "issn": "1520-6106", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry B", "publication_date": "2006-11-16", "series_number": "45", "volume": "110", "issue": "45", "pages": "22732-22735" }, { "id": "authors:4y5a0-j7021", "collection": "authors", "collection_id": "4y5a0-j7021", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PAPprl06", "type": "article", "title": "Absence of Magnetism in Hcp Iron-Nickel at 11 K", "author": [ { "family_name": "Papandrew", "given_name": "A. B.", "clpid": "Papandrew-A-B" }, { "family_name": "Lucas", "given_name": "M. S.", "clpid": "Lucas-M-S" }, { "family_name": "Stevens", "given_name": "R.", "clpid": "Stevens-R" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169", "clpid": "Hu-Michael-Y" }, { "family_name": "Chow", "given_name": "P.", "clpid": "Chow-Paul" }, { "family_name": "Cohen", "given_name": "R. E.", "orcid": "0000-0001-5871-2359", "clpid": "Cohen-R-E" }, { "family_name": "Somayazulu", "given_name": "M.", "clpid": "Somayazulu-M-S" } ], "abstract": "Synchrotron M\u00f6ssbauer spectroscopy (SMS) was performed on an hcp-phase alloy of composition Fe92Ni8 at a pressure of 21 GPa and a temperature of 11 K. Density functional theoretical calculations predict antiferromagnetism in both hcp Fe and hcp Fe-Ni. For hcp Fe, these calculations predict no hyperfine magnetic field, consistent with previous experiments. For hcp Fe-Ni, however, substantial hyperfine magnetic fields are predicted, but these were not observed in the SMS spectra. Two possible explanations are suggested. First, small but significant errors in the generalized gradient approximation density functional may lead to an erroneous prediction of magnetic order or of erroneous hyperfine magnetic fields in antiferromagnetic hcp Fe-Ni. Alternately, quantum fluctuations with periods much shorter than the lifetime of the nuclear excited state would prohibit the detection of moments by SMS.", "doi": "10.1103/PhysRevLett.97.087202", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2006-08-25", "series_number": "8", "volume": "97", "issue": "8", "pages": "Art. No. 087202" }, { "id": "authors:366zs-pk669", "collection": "authors", "collection_id": "366zs-pk669", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DODessl06", "type": "article", "title": "Phase Diagram of Li_xFePO_4", "author": [ { "family_name": "Dodd", "given_name": "J. L.", "clpid": "Dodd-J-L" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phase diagram for LixFePO4 has been determined for different lithium concentrations and temperatures. The two low-temperature phases, heterosite and triphylite, have previously been shown to transform to a disordered solid solution at elevated temperatures. This disordered phase allows for a continuous transition between the heterosite and triphylite phases and is stable at relatively low temperatures. At intermediate temperatures the proposed phase diagram resembles a eutectoid system, with eutectoid point at around x=0.6 and 200\u00b0C. Kinetics of mixing and unmixing transformations are reported, including the hysteresis between heating and cooling. The enthalpy of this transition is at least 700 J/mol.", "doi": "10.1149/1.2164548", "issn": "1099-0062", "publisher": "Electrochemical Society", "publication": "Electrochemical and Solid-State Letters", "publication_date": "2006-03", "series_number": "3", "volume": "9", "issue": "3", "pages": "A151-A155" }, { "id": "authors:51vnb-g9t15", "collection": "authors", "collection_id": "51vnb-g9t15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201005-153617749", "type": "article", "title": "Materials science applications of inelastic neutron scattering", "author": [ { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering measures the dynamical processes in materials, as opposed to spatial arrangements of atoms. A neutron diffraction pattern is obtained from measurements of the momentum transfer between the neutron and the sample. Inelastic neutron scattering includes the additional dimension of energy. This paper explains concepts, describes instrumentation, and gives a few materials applications for inelastic neutron scattering.", "doi": "10.1007/s11837-006-0163-0", "issn": "1047-4838", "publisher": "Springer Boston", "publication": "JOM - Journal of the Minerals, Metals and Materials Society", "publication_date": "2006-03", "series_number": "3", "volume": "58", "issue": "3", "pages": "58-63" }, { "id": "authors:xy2k1-w2a35", "collection": "authors", "collection_id": "xy2k1-w2a35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170711-104503643", "type": "article", "title": "Local Electronic Structure of Layered Li_xNi_(0.5)Mn_(0.5)O_2 and Li_xNi_(1/3)Mn_(1/3)Co_(1/3)O_2", "author": [ { "family_name": "Miao", "given_name": "Shu", "clpid": "Miao-Shu" }, { "family_name": "Kocher", "given_name": "Michael", "clpid": "Kocher-M" }, { "family_name": "Rez", "given_name": "Peter", "clpid": "Rez-P" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ozawa", "given_name": "Yasunori", "clpid": "Ozawa-Yasunori" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" } ], "abstract": "Samples of Li_xNi_(0.5)Mn_(0.5)O_2 and Li_xNi_(1/3)Mn_(1/3)Co_(1/3)O_2 were prepared as active materials in electrochemical half-cells and were cycled electrochemically to obtain different values of Li concentration, x. Absorption edges of Ni, Mn, Co, and O in these materials of differing x were measured by electron energy loss spectrometry (EELS) in a transmission electron microscope to determine the changes in local electronic structure caused by delithiation. The work was supported by electronic structure calculations with the VASP pseudopotential package, the full-potential linear augmented plane wave code WIEN2K, and atomic multiplet calculations that took account of the electronic effects from local octahedral symmetry. A valence change from Ni^(2+) to Ni^(4+) with delithiation would have caused a 3 eV shift in energy of the intense white line at the Ni L_3 edge, but the measured shift was less than 1.2 eV. The intensities of the \"white lines\" at the Ni L-edges did not change enough to account for a substantial change of Ni valence. No changes were detectable at the Mn and Co L-edges after delithiation either. Both EELS and the computational efforts showed that most of the charge compensation for Li^+ takes place at hybridized O 2p states, not at Ni atoms.", "doi": "10.1021/jp0542266", "issn": "1520-6106", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry B", "publication_date": "2005-12-15", "series_number": "49", "volume": "109", "issue": "49", "pages": "23473-23479" }, { "id": "authors:8c8hg-pvz30", "collection": "authors", "collection_id": "8c8hg-pvz30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SWAprb05", "type": "article", "title": "Vibrational entropy of spinodal decomposition in FeCr", "author": [ { "family_name": "Swan-Wood", "given_name": "T. L.", "clpid": "Swan-Wood-T-L" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron-scattering spectra were measured on stoichiometric Fe0.50Cr0.50 prepared as a body-centered-cubic (bcc) solid solution, and after increasing amounts of chemical unmixing on the bcc lattice induced by annealing the solid solution at 773 K. These spectra were reduced by a conventional procedure to a neutron-weighted vibrational density of states. M\u00f6ssbauer spectrometry was used to characterize the extent of decomposition after annealing. A neutron-weight correction was performed, using results from the M\u00f6ssbauer spectra and recent data on inelastic nuclear resonant scattering from 57Fe-Cr. The vibrational entropy of decomposition was found to be \u20130.17\u00b10.01kB/atom, nearly equal to the change in configurational entropy after spinodal decomposition. Effects of vibrational entropy on the thermodynamics of unmixing are analyzed, showing a large effect on the free energy with the formation of Cr-rich zones, and a large effect on the critical temperature for spinodal decomposition for equiatomic Fe0.50Cr0.50.", "doi": "10.1103/PhysRevB.72.024305", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2005-07-01", "series_number": "2", "volume": "72", "issue": "2", "pages": "Art. No. 024305" }, { "id": "authors:0a7cv-h1q92", "collection": "authors", "collection_id": "0a7cv-h1q92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190823-105106859", "type": "article", "title": "Purification of carbon single-wall nanotubes by potassium intercalation and exfoliation", "author": [ { "family_name": "Dailly", "given_name": "A.", "clpid": "Dailly-A" }, { "family_name": "Yim", "given_name": "J. W. L.", "clpid": "Yim-J-W-L" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Miura", "given_name": "E.", "clpid": "Miura-E" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A purification procedure for single-wall carbon nanotubes prepared by the arc-discharge method is described that employs a new step of potassium intercalation. Thermogravimetric analysis, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy were used to characterize the results of each purification step. This potassium intercalation step is particularly useful for exfoliating the graphitic shell structure that typically surrounds the metal catalyst particles that remain from the nanotube synthesis. By exfoliating the shell structure, subsequent treatments are more efficacious for removing the metal catalyst particles. By testing full purification procedures, it is demonstrated that with potassium intercalation the number of purification steps can be reduced.", "doi": "10.1007/s00339-004-3107-y", "issn": "0947-8396", "publisher": "Springer", "publication": "Applied Physics A: Materials Science and Processing", "publication_date": "2005-02", "series_number": "4", "volume": "80", "issue": "4", "pages": "717-722" }, { "id": "authors:f5fdt-e5e23", "collection": "authors", "collection_id": "f5fdt-e5e23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:OZAessl05", "type": "article", "title": "An XRD Study of Chemical Self-Discharge in Delithiated Cobalt Oxide", "author": [ { "family_name": "Ozawa", "given_name": "Yasunori", "clpid": "Ozawa-Yasunori" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Changes in samples of Li1\u2013xCoO2 were measured by X-ray diffractometry (XRD) after thermal aging treatments that cause capacity losses in electrochemical cells. Changes in lattice parameters were used to identify lithium re-intercalation into Li1\u2013xCoO2 when it was aged in the presence of LiClO4, LiPF6, and LiAsF6 in propylene carbonate (PC). Li+ re-intercalation could account for the reversible capacity loss. Thermal aging at 75\u00b0C in pure PC or pure argon gas resulted in other changes that are attributed to the formation of spinel phase. The rate of the lithium re-intercalation increases in the following sequence: LiPF6<LiClO4<LiAsF6.", "doi": "10.1149/1.1830395", "issn": "1099-0062", "publisher": "Electrochemical Society", "publication": "Electrochemical and Solid-State Letters", "publication_date": "2005-01", "series_number": "1", "volume": "8", "issue": "1", "pages": "A38-A41" }, { "id": "authors:b61ak-bwv48", "collection": "authors", "collection_id": "b61ak-bwv48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YUEprl04", "type": "article", "title": "Vibrations of micro-eV energies in nanocrystalline microstructures", "author": [ { "family_name": "Yue", "given_name": "A. F.", "clpid": "Yue-A-F" }, { "family_name": "Papandrew", "given_name": "A. B.", "clpid": "Papandrew-A-B" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Chowdhuri", "given_name": "Z.", "clpid": "Chowdhuri-Z" }, { "family_name": "Dimeo", "given_name": "R. M.", "clpid": "Dimeo-R-M" }, { "family_name": "Neumann", "given_name": "D. A.", "clpid": "Neumann-D-A" } ], "abstract": "The phonon density of states of nanocrystalline bcc Fe and nanocrystalline fcc Ni3Fe were measured by inelastic neutron scattering in two different ranges of energy. As has been reported previously, the nanocrystalline materials showed enhancements in their phonon density of states at energies from 2 to 15 meV, compared to control samples composed of large crystals. The present measurements were extended to energies in the micro-eV range, and showed significant, but smaller, enhancements in the number of modes in the energy range from 5 to 18 mueV. These modes of micro-eV energies provide a long-wavelength limit that bounds the fraction of modes at milli-eV energies originating with the cooperative dynamics of the nanocrystalline microstructure.", "doi": "10.1103/PhysRevLett.93.205501", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2004-11-12", "series_number": "20", "volume": "93", "issue": "20", "pages": "Art. No. 205501" }, { "id": "authors:e9xj1-c1x65", "collection": "authors", "collection_id": "e9xj1-c1x65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:REYprb04", "type": "article", "title": "Entropy of Li intercalation in LixCoO2", "author": [ { "family_name": "Reynier", "given_name": "Yvan", "clpid": "Reynier-Y" }, { "family_name": "Graetz", "given_name": "Jason", "clpid": "Graetz-J" }, { "family_name": "Swan-Wood", "given_name": "Tabitha", "clpid": "Swan-Wood-T-L" }, { "family_name": "Rez", "given_name": "Peter", "clpid": "Rez-P" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The entropy of lithiation of LixCoO2 for 0.5 < x less than or equal to 1.0 was determined from measurements of the temperature dependence of equilibrated voltages of electrochemical cells. Measured changes in the entropy of the lithiation reaction were as large as 9.0 k(B)/atom, and as large as 4.2 k(B)/atom within the \"O3\" layered hexagonal structure of LixCoO2. Three contributions to the entropy of lithiation for the O3 phase were assessed by experiment and calculation. The phonon entropy of lithiation was determined from measurements of inelastic neutron scattering. Phonon entropy can account for much of the negative entropy of lithiation, but its changes with lithium concentration were found to be small. Electronic structure calculations in the local density approximation gave a small electronic entropy of lithiation of the O3 phase. The configurational entropy from lithium-vacancy disorder was large enough to account for most of the compositional trend in the entropy of lithiation of the O3 phase if ordered structures exist at lithium concentrations of x=1/2 and x=5/6. The electrochemical measurements showed the existence of a two-phase region in the composition range between x=5/6 and 0.95. Electronic structure calculations gave evidence that these phases were metallic and insulating, respectively. Changes of the electronic and configurational entropy were found to be of comparable importance for this metal-insulator transition.", "doi": "10.1103/PhysRevB.70.174304", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2004-11-01", "series_number": "17", "volume": "70", "issue": "17", "pages": "Art. No. 174304" }, { "id": "authors:j5czr-4zm39", "collection": "authors", "collection_id": "j5czr-4zm39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DELprl04", "type": "article", "title": "Negative Entropy of Mixing for Vanadium-Platinum Solutions", "author": [ { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Swan-Wood", "given_name": "T.", "clpid": "Swan-Wood-T-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The phonon densities of states for pure vanadium and the solid solutions V-6.25% Ni, Pd, Pt were determined from inelastic neutron scattering measurements. The solute atoms caused a large stiffening of the phonons, resulting in large, negative vibrational entropies of mixing. For V-6.25%Pt, the negative vibrational entropy of mixing exceeds the conventional positive chemical entropy of mixing. This negative total entropy of mixing should extend to lower concentrations of Pt, and the effect on the bcc solvus line is discussed. The experimental data were inverted to obtain interatomic force constants by using a Born\u2013von K\u00e1rm\u00e1n model with an iterative optimization algorithm. The stiffening of bonds responsible for the decrease of entropy was found to occur mainly in first-nearest-neighbor solute-host bonds, and correlates in part with the solute metallic radius.", "doi": "10.1103/PhysRevLett.93.185704", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2004-10-29", "series_number": "18", "volume": "93", "issue": "18", "pages": "Art. No. 185704" }, { "id": "authors:wxyjh-p0n51", "collection": "authors", "collection_id": "wxyjh-p0n51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170524-113943677", "type": "article", "title": "Altering Hydrogen Storage Properties by Hydride Destabilization through Alloy Formation: LiH and MgH_2 Destabilized with Si", "author": [ { "family_name": "Vajo", "given_name": "John J.", "orcid": "0000-0002-6271-4899", "clpid": "Vajo-J-J" }, { "family_name": "Mertens", "given_name": "Florian", "clpid": "Mertens-F" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Bowman", "given_name": "Robert C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH_2. For the LiH/Si system, a Li_(2.35)Si alloy forms upon dehydrogenation, causing the equilibrium hydrogen pressure at 490 \u00b0C to increase from approximately 5 \u00d7 10^(-5) to 1 bar. For the MgH_2/Si system, Mg_2_Si forms upon dehydrogenation, causing the equilibrium pressure at 300 \u00b0C to increase from 1.8 to >7.5 bar. Thermodynamic calculations indicate equilibrium pressures of 1 bar at approximately 20 \u00b0C and 100 bar at approximately 150 \u00b0C. These conditions indicate that the MgH2/Si system, which has a hydrogen capacity of 5.0 wt %, could be practical for hydrogen storage at reduced temperatures. The LiH/Si system is reversible and can be cycled without degradation. Absorption/desorption isotherms, obtained at 400\u2212500 \u00b0C, exhibited two distinct flat plateaus with little hysteresis. The plateaus correspond to formation and decomposition of various Li silicides. The MgH2/Si system was not readily reversible. Hydrogenation of Mg2Si appears to be kinetically limited because of the relatively low temperature, <150 \u00b0C, required for hydrogenation at 100 bar. These two alloy systems show how hydride destabilization through alloy formation upon dehydrogenation can be used to design and control equilibrium pressures of strongly bound hydrides.", "doi": "10.1021/jp040060h", "issn": "1520-6106", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry B", "publication_date": "2004-09-16", "series_number": "37", "volume": "108", "issue": "37", "pages": "13977-13983" }, { "id": "authors:3bw4s-fc755", "collection": "authors", "collection_id": "3bw4s-fc755", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GRAprb04", "type": "article", "title": "White lines and d-band occupancy for the 3d transition-metal oxides and lithium transition-metal oxides", "author": [ { "family_name": "Graetz", "given_name": "Jason", "clpid": "Graetz-J" }, { "family_name": "Ahn", "given_name": "Channing C.", "clpid": "Ahn-C-C" }, { "family_name": "Ouyang", "given_name": "Hao", "clpid": "Ouyang-Hao" }, { "family_name": "Rez", "given_name": "Peter", "clpid": "Rez-P" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Electron energy-loss spectrometry was employed to measure the white lines at the L-2,L-3 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L-3/L-2) was found to increase between d(0) and d(5), and decrease between d(5) and d(10), consistent with previous results for the transition metals and their oxides. The intensities of the white lines, normalized to the post-edge background, are linear for the 3d transition-metal and lithium transition-metal oxides. An empirical correlation between normalized white-line intensity and 3d occupancy is established. It provides a method for measuring changes in the 3d-state occupancy. As an example, this empirical relationship is used to measure changes in the transition-metal valences of Li1-xNi0.8Co0.2O2 in the range of 0less than or equal toxless than or equal to0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.", "doi": "10.1103/PhysRevB.69.235103", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2004-06", "series_number": "23", "volume": "69", "issue": "23", "pages": "Art. No. 235103" }, { "id": "authors:wfpfc-k9y89", "collection": "authors", "collection_id": "wfpfc-k9y89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GABjes04", "type": "article", "title": "Hexagonal to Cubic Spinel Transformation in Lithiated Cobalt Oxide", "author": [ { "family_name": "Gabrisch", "given_name": "Heike", "clpid": "Gabrisch-H" }, { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A transmission electron microscopy (TEM) investigation was performed on LiCoO2 before and after it had been subjected to charge/discharge cycling in electrochemical cells, as well as on delithiated Li(1\u2013x)CoO2 before and after thermal aging. Turbostratic disorder involving small rotations of the O-Co-O slabs was found in as-received material, and in material subjected to a few cycles. In LiCoO2 subjected to extensive charge/discharge cycling, it was found that increasing amounts of the trigonal O3 phase had transformed to H1-3 phase and to the cubic spinel phase. The transformation appears to initiate on the surfaces of trigonal crystals. The orientation relationship between the trigonal and spinel phases was determined from diffraction patterns to be {0001}trigonal parallel {111}cubic and <112-bar 0>trigonal parallel <110>cubic. The difference in unit cell dimensions leads to transformation stresses when spinel crystals are formed, and spallation of surface layers was observed. The formation of a spinel phase could suppress electrochemical performance of LiCoO2 cathodes in heavily cycled cells. Aging in the charged state also can alter particle surfaces and therefore the performance.", "doi": "10.1149/1.1738677", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2004-06", "series_number": "6", "volume": "151", "issue": "6", "pages": "A891-A897" }, { "id": "authors:qsc0q-mq262", "collection": "authors", "collection_id": "qsc0q-mq262", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GRAjes04", "type": "article", "title": "Nanocrystalline and Thin Film Germanium Electrodes with High Lithium Capacity and High Rate Capabilities", "author": [ { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Germanium nanocrystals (12 nm mean diam) and amorphous thin films (60-250 nm thick) were prepared as anodes for lithium secondary cells. Amorphous thin film electrodes prepared on planar nickel substrates showed stable capacities of 1700 mAh/g over 60 cycles. Germanium nanocrystals showed reversible gravimetric capacities of up to 1400 mAh/g with 60% capacity retention after 50 cycles. Both electrodes were found to be crystalline in the fully lithiated state. The enhanced capacity, rate capability (1000C), and cycle life of nanophase germanium over bulk crystalline germanium is attributed to the high surface area and short diffusion lengths of the active material and the absence of defects in nanophase materials.", "doi": "10.1149/1.1697412", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2004-05", "series_number": "5", "volume": "151", "issue": "5", "pages": "A698-A702" }, { "id": "authors:sgdch-g9834", "collection": "authors", "collection_id": "sgdch-g9834", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MCQprl04", "type": "article", "title": "Unusual phonon softening in delta-phase plutonium", "author": [ { "family_name": "McQueeney", "given_name": "R. J.", "clpid": "McQueeney-R-J" }, { "family_name": "Lawson", "given_name": "A. C.", "clpid": "Lawson-A-C" }, { "family_name": "Migliori", "given_name": "A.", "clpid": "Migliori-A" }, { "family_name": "Kelley", "given_name": "T. M.", "clpid": "Kelley-T-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ramos", "given_name": "M.", "clpid": "Ramos-M" }, { "family_name": "Martinez", "given_name": "B.", "clpid": "Martinez-B" }, { "family_name": "Lashley", "given_name": "J. C.", "clpid": "Lashley-J-C" }, { "family_name": "Vogel", "given_name": "S. C.", "clpid": "Vogel-S-C" } ], "abstract": "The phonon density of states and adiabatic sound velocities were measured on fcc-stabilized (242)pu(0.95)Al(0.05). The phonon frequencies and sound velocities decrease considerably (soften) with increasing temperature despite negligible thermal expansion. The frequency softening of the transverse branch along the [111] direction is anomalously large (similar to 30%) and is very sensitive to alloy composition. The large magnitude of the phonon softening is not observed in any other fcc metals and may arise from an unusual temperature dependence of the electronic structure in this narrow 5f-band metal.", "doi": "10.1103/PhysRevLett.92.146401", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2004-04-09", "series_number": "14", "volume": "92", "issue": "14", "pages": "Art. No. 146401" }, { "id": "authors:8k4ek-1q207", "collection": "authors", "collection_id": "8k4ek-1q207", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PAPprb04", "type": "article", "title": "Vibrational modes in nanocrystalline iron under high pressure", "author": [ { "family_name": "Papandrew", "given_name": "Alexander B.", "clpid": "Papandrew-A-B" }, { "family_name": "Yue", "given_name": "Alan F.", "clpid": "Yue-Alan-F" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Halevy", "given_name": "Itzhak", "clpid": "Halevy-I" }, { "family_name": "Sturhahn", "given_name": "Wolfgang", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Toellner", "given_name": "Thomas S.", "clpid": "Toellner-T-S" }, { "family_name": "Alp", "given_name": "E. Ercan", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Mao", "given_name": "Ho-kwang", "clpid": "Mao-Ho-kwang" } ], "abstract": "The phonon density of states (DOS) of nanocrystalline 57Fe was measured using nuclear resonant inelastic x-ray scattering (NRIXS) at pressures up to 28 GPa in a diamond anvil cell. The nanocrystalline material exhibited an enhancement in its DOS at low energies by a factor of 2.2. This enhancement persisted throughout the entire pressure range, although it was reduced to about 1.7 after decompression. The low-energy regions of the spectra were fitted to the function AEn, giving values of n close to 2 for both the bulk control sample and the nanocrystalline material, indicative of nearly three-dimensional vibrational dynamics. At higher energies, the van Hove singularities observed in both samples were coincident in energy and remained so at all pressures, indicating that the forces conjugate to the normal coordinates of the nanocrystalline materials are similar to the interatomic potentials of bulk crystals.", "doi": "10.1103/PhysRevB.69.144301", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2004-04-01", "series_number": "14", "volume": "69", "issue": "14", "pages": "Art. No. 144301" }, { "id": "authors:pya8d-k3w66", "collection": "authors", "collection_id": "pya8d-k3w66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180810-142641189", "type": "article", "title": "Spatial periodicities of defect environments in ^(57)Fe_3Al studied by M\u00f6ssbauer powder diffractometry", "author": [ { "family_name": "Lin", "given_name": "Jiao Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "M\u00f6ssbauer powder diffractometry was used to study partially-ordered ^(57)Fe_3Al. Multiple diffraction patterns were measured at Doppler velocities across all nuclear resonances in the sample. The superlattice diffractions were analyzed to provide data on the long-range order of Fe atoms having different numbers of Al neighbors. Comparing experimental data to calculations showed that Fe atoms having three Al atoms as first-nearest neighbors (1nn) have simple cubic long-range order, similar to that of Fe atoms with four Al 1nn. The simple cubic periodicity of Fe atoms with three Al 1nn was significantly lower than expected for homogeneous antisite disorder, however. Monte-Carlo simulations and transmission electron microscopy suggest that a significant fraction of aperiodic Fe atoms with three Al 1nn are near antiphase domain boundaries.", "doi": "10.1524/zkri.219.3.172.29095", "issn": "2194-4946", "publisher": "Oldenbourg Wissenschaftsverlag", "publication": "Zeitschrift f\u00fcr Kristallographie - Crystalline Materials", "publication_date": "2004-03", "series_number": "3", "volume": "219", "issue": "3", "pages": "172-178" }, { "id": "authors:6nmrn-e2m11", "collection": "authors", "collection_id": "6nmrn-e2m11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:REYjes04", "type": "article", "title": "Thermodynamics of Lithium Intercalation into Graphites and Disordered Carbons", "author": [ { "family_name": "Reynier", "given_name": "Y. F.", "clpid": "Reynier-Y-F" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The temperature dependence of the open-circuit potential of lithium half-cells was measured for electrodes of carbon materials having different amounts of structural disorder. The entropy of lithium intercalation, DeltaS, and enthalpy of intercalation, DeltaH, were determined over a broad range of lithium concentrations. For the disordered carbons, DeltaS is small. For graphite, an initially large DeltaS decreases with lithium concentration, becomes negative, and then shows two plateaus associated with the formation of intercalation compounds. For all carbons DeltaH is negative, and decreases in magnitude with increased lithium concentration. For lithium concentrations less than x = 0.5 in LixC6, for the disordered carbons the magnitude of DeltaH is significantly more negative than for graphite (i.e., intercalation is more exothermic). The measurements of DeltaH provide an energy spectrum of chemical environments for lithium. This spectrum can be used to understand some of the concentration dependence of configurational entropy, but the negative values of DeltaS require another contribution to entropy, perhaps vibrational in origin.", "doi": "10.1149/1.1646152", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2004-03", "series_number": "3", "volume": "151", "issue": "3", "pages": "A422-A426" }, { "id": "authors:6a5pk-weg52", "collection": "authors", "collection_id": "6a5pk-weg52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GRAessl03", "type": "article", "title": "Highly Reversible Lithium Storage in Nanostructured Silicon", "author": [ { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Anode materials of nanostructured silicon have been prepared by physical vapor deposition and characterized using electrochemical methods. The electrodes were prepared in thin-film form as nanocrystalline particles (12 nm mean diameter) and as continuous amorphous thin films (100 nm thick). The nanocrystalline silicon exhibited specific capacities of around 1100 mAh/g with a 50% capacity retention after 50 cycles. The amorphous thin-film electrodes exhibited initial capacities of 3500 mAh/g with a stable capacity of 2000 mAh/g over 50 cycles. We suggest that the nanoscale dimensions of the silicon circumvents conventional mechanisms of mechanical deterioration, permitting good cycle life.", "doi": "10.1149/1.1596917", "issn": "1099-0062", "publisher": "Electrochemical Society", "publication": "Electrochemical and Solid-State Letters", "publication_date": "2003-09", "series_number": "9", "volume": "6", "issue": "9", "pages": "A194-A197" }, { "id": "authors:yf5wz-pmp06", "collection": "authors", "collection_id": "yf5wz-pmp06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BOGprb03", "type": "article", "title": "Phonon entropy of alloying and ordering of Cu-Au", "author": [ { "family_name": "Bogdanoff", "given_name": "P. D.", "clpid": "Bogdanoff-P-D" }, { "family_name": "Swan-Wood", "given_name": "T. L.", "clpid": "Swan-Wood-T-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Inelastic neutron scattering spectra were measured with a time-of-flight spectrometer on six disordered Cu-Au alloys at 300 K. The neutron-weighted phonon density of states was obtained from a conventional analysis of these spectra. Several methods were developed to account for this neutron weighting and obtain the phonon entropy of the disordered alloys. The phonon entropies of formation of disordered fcc Cu-Au alloys obtained in this way were generally mutually consistent, and were also consistent with predictions from a cluster approximation obtained from ab-initio calculations by Ozolin[underaccent cedilla [below] s-breve, Wolverton, and Zunger. We estimate a phonon entropy of disordering of 0.15\u00b10.05kB/atom in Cu3Au at 300 K. A resonance mode associated with the motions of the heavy Au atoms in the Cu-rich alloys was observed at 9 meV. An analysis of the resonance mode provided a check on the partial phonon entropy of Au atoms.", "doi": "10.1103/PhysRevB.68.014301", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2003-07-01", "series_number": "1", "volume": "68", "issue": "1", "pages": "Art. No. 014301" }, { "id": "authors:ybxqs-pep15", "collection": "authors", "collection_id": "ybxqs-pep15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170519-142726956", "type": "article", "title": "An Electron Energy-Loss Spectrometry Study of Charge Compensation in LiNi_(0.8)Co_(0.2)O_2", "author": [ { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Changes in the electronic structure of Li_(1-x)Ni_(0.8)Co_(0.2)O_2 during delithiation (charge) are elucidated by changes in the O K-edge and transition-metal (TM) L_(2,3)-edge. Electron energy-loss spectrometry was used to investigate the O 2p and TM 3d occupancy over a wide range of lithium concentrations. Quantitative analysis of the TM L_(2,3) white lines indicates that the Ni ion accommodates no more than one-half of an electron, whereas the net Co valence is unaffected by delithiation. In contrast with the small changes observed in the TM L_(2,3)-edge, a large decrease in state occupancy is observed in the near-edge structure of the O K-edge, suggesting that much of the electron charge is accommodated by the anion.", "doi": "10.1021/jp026484y", "issn": "1520-6106", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry B", "publication_date": "2003-04-03", "series_number": "13", "volume": "107", "issue": "13", "pages": "2887-2891" }, { "id": "authors:jvh4m-ptm90", "collection": "authors", "collection_id": "jvh4m-ptm90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MANprb03", "type": "article", "title": "No role for phonon entropy in the fcc -> fcc volume collapse transition in Ce0.9Th0.1 at ambient pressure", "author": [ { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-M-E" }, { "family_name": "McQueeney", "given_name": "R. J.", "clpid": "McQueeney-R-J" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Swan-Wood", "given_name": "T.", "clpid": "Swan-Wood-T-L" }, { "family_name": "Delaire", "given_name": "O.", "clpid": "Delaire-O" }, { "family_name": "Goremychkin", "given_name": "E. A.", "clpid": "Goremychkin-E-A" }, { "family_name": "Cooley", "given_name": "J. C.", "clpid": "Cooley-J-C" }, { "family_name": "Hults", "given_name": "W. L.", "clpid": "Hults-W-L" }, { "family_name": "Lashley", "given_name": "J. C.", "clpid": "Lashley-J-C" }, { "family_name": "Osborn", "given_name": "R.", "clpid": "Osborn-R" }, { "family_name": "Smith", "given_name": "J. L.", "clpid": "Smith-J-L" } ], "abstract": "Phonon densities of states (DOS) were obtained from inelastic neutron scattering measurements on Ce0.9Th0.1 at temperatures from 10 to 300 K. The alpha phase showed a significant softening of its phonon DOS when heated from 10 to 140 K. Despite the 17% volume collapse, the phonon DOS showed little change between the gamma phase at 150 K and the alpha phase at 140 K. This is supported by analysis of the magnetic spectra showing that most of the transition entropy can be accounted for with the crystal field and changes in the ground-state spin fluctuations. We argue that the anomalous behavior of the phonon DOS originates with the volume dependence of the ground-state spin fluctuations.", "doi": "10.1103/PhysRevB.67.014103", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2003-01-01", "series_number": "1", "volume": "67", "issue": "1", "pages": "Art. no. 014103" }, { "id": "authors:m02pc-hjb96", "collection": "authors", "collection_id": "m02pc-hjb96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111026-150332804", "type": "article", "title": "Metallic Hydrides I: Hydrogen Storage and Other Gas-Phase Applications", "author": [ { "family_name": "Bowman", "given_name": "Robert C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A brief survey is given of the various classes of metal alloys and compounds that are suitable for hydrogen-storage and energy-conversion applications. Comparisons are made of relevant properties including hydrogen absorption and desorption pressures, total and reversible hydrogen-storage capacity, reaction-rate kinetics, initial activation requirements, susceptibility to contamination, and durability during long-term thermal cycling. Selected applications are hydrogen storage as a fuel, gas separation and purification, thermal switches, and sorption cryocoolers.", "doi": "10.1557/mrs2002.223", "issn": "0883-7694", "publisher": "Materials Research Society", "publication": "MRS Bulletin", "publication_date": "2002-09", "series_number": "9", "volume": "27", "issue": "9", "pages": "688-693" }, { "id": "authors:pj8ha-4z550", "collection": "authors", "collection_id": "pj8ha-4z550", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MANprb02b", "type": "article", "title": "Microstructural strain energy of \u03b1-uranium determined by calorimetry and neutron diffractometry", "author": [ { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-M-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Brown", "given_name": "D. W.", "clpid": "Brown-D-W" }, { "family_name": "Clausen", "given_name": "B.", "clpid": "Clausen-B" }, { "family_name": "Lawson", "given_name": "A. C.", "clpid": "Lawson-A-C" }, { "family_name": "Cooley", "given_name": "J. C.", "clpid": "Cooley-J-C" }, { "family_name": "Hults", "given_name": "W. L.", "clpid": "Hults-W-L" }, { "family_name": "Hanrahan", "given_name": "R. J., Jr.", "clpid": "Hanrahan-R-J" }, { "family_name": "Smith", "given_name": "J. L.", "clpid": "Smith-J-L" }, { "family_name": "Thoma", "given_name": "D. J.", "clpid": "Thoma-D-J" } ], "abstract": "The microstructural contribution to the heat capacity of \u03b1-uranium was determined by measuring the heat-capacity difference between polycrystalline and single-crystal samples from 77 to 320 K. When cooled to 77 K and then heated to about 280 K, the uranium microstructure released (3\u00b11) J/mol of strain energy. On further heating to 300 K, the microstructure absorbed energy as it began to redevelop microstrains. Anisotropic strain-broadening parameters were extracted from neutron-diffraction measurements on polycrystals. Combining the strain-broadening parameters with anisotropic elastic constants from the literature, the microstructural strain energy is predicted in the two limiting cases of statistically isotropic stress and statistically isotropic strain. The result calculated in the limit of statistically isotropic stress was (3.7\u00b10.5) J/mol K at 77 K and (1\u00b10.5) J/mol at room temperature. In the limit of statistically isotropic strain, the values were (7.8\u00b10.5) J/mol K at 77 K and (4.5\u00b10.5) J/mol at room temperature. In both cases the changes in the microstructural strain energy showed good agreement with the calorimetry.", "doi": "10.1103/PhysRevB.66.024117", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-07-01", "series_number": "2", "volume": "66", "issue": "2", "pages": "Art. No. 024117" }, { "id": "authors:bz3tw-71x47", "collection": "authors", "collection_id": "bz3tw-71x47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GABessl02", "type": "article", "title": "The Character of Dislocations in LiCoO2", "author": [ { "family_name": "Gabrisch", "given_name": "H.", "clpid": "Gabrisch-H" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Dislocations in LiCoO2 were observed by transmission electron microscopy, and their Burgers vectors were determined by analysis of diffraction contrast in tilting experiments. The configuration of all dislocations indicates that they are glissile, and dislocation configurations were found that are indicative of active slip planes. Perfect dislocations of a/3<112-bar 0> type Burgers vectors were observed on {0001} habit planes. These perfect dislocations sometimes dissociate into Shockley partial dislocations with a/3<101-bar 0> type Burgers vectors. Glide of these partial dislocations can account for the sequence of crystal structures O3, H1-3, O1 that occur with the delithiation of LiCoO2. The presence of glissile dislocations also suggests possible damage mechanisms during cycling.", "doi": "10.1149/1.1472257", "issn": "1099-0062", "publisher": "Electrochemical Society", "publication": "Electrochemical and Solid-State Letters", "publication_date": "2002-06", "series_number": "6", "volume": "5", "issue": "6", "pages": "A111-A114" }, { "id": "authors:c49rm-80z90", "collection": "authors", "collection_id": "c49rm-80z90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190829-131534125", "type": "article", "title": "Mass Effects on Optical Phonons in L1_2-Ordered Pt_3^(57)Fe and Pd_3^(57)Fe", "author": [ { "family_name": "Yue", "given_name": "A. F.", "clpid": "Yue-Alan-F" }, { "family_name": "Papandrew", "given_name": "A.", "clpid": "Papandrew-A-B" }, { "family_name": "Bogdanoff", "given_name": "P. D.", "clpid": "Bogdanoff-P-D" }, { "family_name": "Halevy", "given_name": "I.", "clpid": "Halevy-I" }, { "family_name": "Lin", "given_name": "J. G.-W.", "clpid": "Lin-J-G-W" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Alp", "given_name": "E. E.", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Toellner", "given_name": "T. S.", "clpid": "Toellner-T-S" } ], "abstract": "Inelastic nuclear resonant scattering spectra of ^(57)Fe atoms were measured on Pt_3^(57)Fe and Pd_3^(57)Fe with the L1_2 crystal structure, and with the same crystallographic sites for ^(57)Fe atoms. Phonon partial density of states curves for ^(57)Fe were obtained from these spectra. In comparison to the non-dispersive Einstein-like optical modes in Pt_3^(57)Fe, the optical modes in Pd_3^(57)Fe are broader. This difference can be understood in terms of the difference in mass of Pd and Pt.", "doi": "10.1023/a:1021295112714", "issn": "0304-3843", "publisher": "Springer Nature", "publication": "Hyperfine Interactions", "publication_date": "2002-06", "series_number": "1/4", "volume": "141/142", "issue": "1/4", "pages": "249-253" }, { "id": "authors:1r0gz-3k808", "collection": "authors", "collection_id": "1r0gz-3k808", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GOOjap02", "type": "article", "title": "Magnetomechanical damping by polycrystalline TbDy", "author": [ { "family_name": "Good", "given_name": "N.", "clpid": "Good-N" }, { "family_name": "Dooley", "given_name": "J.", "clpid": "Dooley-J-A" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Vibration damping in polycrystalline TbDy alloys was studied at cryogenic temperatures. Mechanical hysteretic losses were measured at various strains, frequencies, and loading configurations at 77 K. Some textured TbDy materials demonstrated 22.6% energy dissipation in mechanical measurements at low frequency (0.01 Hz) and a mean logarithmic decrement of 0.23 at a higher frequency (25 kHz). Ultrasonic velocities of longitudinal and shear elastic waves were measured on single and polycrystalline TbDy; little variation in ultrasonic velocities was found even for samples with large variation in crystallographic texture and magnetomechanical properties.", "doi": "10.1063/1.1452217", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2002-05-15", "series_number": "10", "volume": "91", "issue": "10", "pages": "7824-7826" }, { "id": "authors:0x8tb-8av11", "collection": "authors", "collection_id": "0x8tb-8av11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MANprb02a", "type": "article", "title": "Vibrational and electronic entropy of \u03b2-cerium and \u03b3-cerium measured by inelastic neutron scattering", "author": [ { "family_name": "Manley", "given_name": "Michael E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-M-E" }, { "family_name": "McQueeney", "given_name": "Robert J.", "clpid": "McQueeney-R-J" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Osborn", "given_name": "Raymond", "clpid": "Osborn-R" }, { "family_name": "Kwei", "given_name": "George H.", "clpid": "Kwei-George-H" }, { "family_name": "Bogdanoff", "given_name": "Peter D.", "clpid": "Bogdanoff-P-D" } ], "abstract": "Time-of-flight (TOF) inelastic neutron-scattering spectra were measured on \u03b2-cerium (double hcp) and \u03b3-cerium (fcc) near the phase-transition temperature. Phonon densities of states (DOS) and crystal-field levels were extracted from the TOF spectra. A softening of the phonon DOS occurs in the transition from \u03b2- to \u03b3-cerium, accounting for an increase in vibrational entropy of \u0394Svib\u03b3-\u03b2=(0.09\u00b10.05)kB/atom. The entropy calculated from the crystal-field levels and a fit to calorimetry data from the literature were significantly larger in \u03b2-cerium than in \u03b3-cerium below room temperature, but the difference was found to be negligible at the experimental phase-transition temperature. A contribution to the specific heat from Kondo spin fluctuations was consistent with the quasielastic magnetic scattering, but the difference between phases was negligible. To be consistent with the latent heat of the \u03b2-\u03b3 transition, the increase in vibrational entropy at the phase transition may be accompanied by a decrease in electronic entropy not associated with the crystal-field splitting or spin fluctuations. At least three sources of entropy need to be considered for the \u03b2-\u03b3 transition in cerium.", "doi": "10.1103/PhysRevB.65.144111", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-04-01", "series_number": "14", "volume": "65", "issue": "14", "pages": "Art. No. 144111" }, { "id": "authors:sq138-hvk29", "collection": "authors", "collection_id": "sq138-hvk29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200224-154418263", "type": "article", "title": "A M\u00f6ssbauer Effect Powder Diffractometer", "author": [ { "family_name": "Kriplani", "given_name": "U.", "clpid": "Kriplani-U" }, { "family_name": "Regehr", "given_name": "M. W.", "clpid": "Regehr-M-W" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "An automated, high-sensitivity M\u00f6ssbauer powder diffractometer is described, and its performance demonstrated with a bcc \u2075\u2077Fe foil sample. Useful diffraction patterns are acquired in about 10 hours. The incoherent and coherent parts of the scattering are readily identified. Both are affected by thickness distortion, but the incoherent part is affected more strongly.", "doi": "10.1023/a:1021299517850", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "2002-03", "series_number": "1-4", "volume": "139-140", "issue": "1-4", "pages": "667-672" }, { "id": "authors:r97je-dg711", "collection": "authors", "collection_id": "r97je-dg711", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170616-134646937", "type": "article", "title": "Electronic Structure of Chemically-Delithiated LiCoO_2 Studied by Electron Energy-Loss Spectrometry", "author": [ { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Yazami", "given_name": "R.", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-Rachid" }, { "family_name": "Rez", "given_name": "P.", "clpid": "Rez-P" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The electronic structure of chemically delithiated Li_(1-x)CoO_2 (x = \u22120.02, 0.09, 0.12, 0.20, and 0.28) was investigated by electron energy-loss spectrometry (EELS). The O K edge and Co L_(2,3) edge were used to probe the density of unoccupied states around the O and Co ions at different states of lithiation. The O ions accommodate the incoming charge during Li intercalation. The net electron density surrounding the Co ions is less affected. This is in substantial agreement with prior electronic structure calculations of Van der Ven, et al., whose atomic structure data were used in the present calculations of EELS cross-sections. Calculations of the O 2p partial densities of state curves confirm the increase in unoccupied states that accompany Li extraction.", "doi": "10.1021/jp0133283", "issn": "1520-6106", "publisher": "American Chemical Society", "publication": "Journal of Physical Chemistry B", "publication_date": "2002-02-14", "series_number": "6", "volume": "106", "issue": "6", "pages": "1286-1289" }, { "id": "authors:bf8vy-h3705", "collection": "authors", "collection_id": "bf8vy-h3705", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb02", "type": "article", "title": "M\u00f6ssbauer diffractometry on polycrystalline (57)Fe3Al", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Stephens", "given_name": "T. A.", "clpid": "Stephens-T-A" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Kriplani", "given_name": "U.", "clpid": "Kriplani-U" } ], "abstract": "A Mossbauer powder diffractometer was used to measure diffraction patterns from polycrystalline foils of (Fe3Al)-Fe-57. The intensities of Bragg diffractions were measured as a function of the energy of the incident photon. The bee fundamental diffractions showed large changes in intensity as the incident energy was tuned through the nuclear resonances. These variations of diffraction intensity with incident energy were calculated with reasonable success using a kinematical theory of diffraction that included effects of coherent interference between x-ray Rayleigh scattering and, more importantly for these samples, Mossbauer scattering from nuclei having different hyperfine magnetic fields.", "doi": "10.1103/PhysRevB.65.064419", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-02-01", "series_number": "6", "volume": "65", "issue": "6", "pages": "Art. No. 064419" }, { "id": "authors:sszvd-zfg03", "collection": "authors", "collection_id": "sszvd-zfg03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BOGprb02", "type": "article", "title": "Temperature dependence of the phonon entropy of vanadium", "author": [ { "family_name": "Bogdanoff", "given_name": "P. D.", "clpid": "Bogdanoff-P-D" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" }, { "family_name": "Crow", "given_name": "L.", "clpid": "Crow-L" } ], "abstract": "The phonon density-of-states (DOS) of elemental vanadium was measured at elevated temperatures by inelastic neutron scattering. The phonon softening predicted by thermal expansion against the bulk modulus is much larger than the measured shifts in phonon energies. We conclude that the phonon anharmonicities associated with thermal expansion are largely canceled by effects from phonon-phonon scattering. Prior measurements of the heat capacity and calculations of the electronic entropy of vanadium are assessed, and consistency requires an explicit temperature dependence of the phonon DOS. Using data from the literature, similar results are found for chromium, niobium, titanium, and zirconium.", "doi": "10.1103/PhysRevB.65.014303", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-01-01", "series_number": "1", "volume": "65", "issue": "1", "pages": "Art. No. 014303" }, { "id": "authors:xfjep-35327", "collection": "authors", "collection_id": "xfjep-35327", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ZILprb02", "type": "article", "title": "Metastable and transient states of chemical ordering in Fe-V nanocrystalline alloys", "author": [ { "family_name": "Ziller", "given_name": "T.", "clpid": "Ziller-T" }, { "family_name": "Le Ca\u00ebr", "given_name": "G.", "clpid": "Le-Ca\u00ebr-G" }, { "family_name": "Isnard", "given_name": "O.", "clpid": "Isnard-O" }, { "family_name": "C\u00e9n\u00e9d\u00e8se", "given_name": "P.", "clpid": "C\u00e9n\u00e9d\u00e8se-P" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Chemical ordering of the disordered alloys Fe0.78V0.22, Fe0.53V0.47, Fe0.39V0.61, and Fe0.37V0.63 was performed by annealing at temperatures from 723 to 973 K. The initial state of chemical disorder was produced by high-energy ball milling, and the evolution of order was measured by neutron diffractometry and by 57Fe M\u00f6ssbauer spectrometry. The hyperfine magnetic field distributions obtained from the M\u00f6ssbauer spectra provided quantitative measurements of the number of antisite Fe atoms in the partially ordered alloys. The long-range order parameters in steady state after long annealing times were used as states of metastable equilibrium for a generally successful comparison with the metastable Fe-V phase diagram calculated by Sanchez et al. [Phys. Rev. B 54, 8958 (1996)]. For the metastable equilibrium state of order in Fe0.53V0.47 at low temperatures, the order parameters were smaller than expected. This corresponded to an abundance of antisite atoms, which were not removed effectively by annealing at the lower temperatures.", "doi": "10.1103/PhysRevB.65.024204", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-01-01", "series_number": "2", "volume": "65", "issue": "2", "pages": "Art. No. 024204" }, { "id": "authors:532vt-30895", "collection": "authors", "collection_id": "532vt-30895", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KRIprb02", "type": "article", "title": "Intensities of M\u00f6ssbauer diffractions from polycrystalline bcc Fe-57", "author": [ { "family_name": "Kriplani", "given_name": "U.", "clpid": "Kriplani-U" }, { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Regehr", "given_name": "M. W.", "clpid": "Regehr-M-W" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Diffraction patterns were measured on a polycrystalline bcc 57Fe foil using a M\u00f6ssbauer powder diffractometer with high sensitivity. Measurements with and without a magnetic field normal to the scattering plane showed large differences in the diffracted intensities of the different nuclear resonances. These magnetic effects on diffraction intensities were interpreted successfully with a single scattering theory developed to handle isotropic and anisotropic orientation distributions of hyperfine magnetic fields. When there is coherent interference between nuclear scattering and x-ray Rayleigh scattering, an asymmetry in the coherent intensity of the three pairs of diffractions for the 57Fe magnetic sextet (1,6), (2,5), (3,4) is predicted. This is largest in the presence of a uniaxial magnetic field, and the calculated and measured asymmetries were in good agreement. A reduced diffraction intensity for lines (2,5) and (3,4) caused by spin-flip incoherence was also measured. The effects of dynamical diffraction, if present, are shown to be small.", "doi": "10.1103/PhysRevB.65.024405", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2002-01-01", "series_number": "2", "volume": "65", "issue": "2", "pages": "Art. No. 024405" }, { "id": "authors:2d2mg-gax22", "collection": "authors", "collection_id": "2d2mg-gax22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YAZjcp01", "type": "article", "title": "Self-organized carbon nanostrips with a new LiC10 structure derived from carbon nanotubes", "author": [ { "family_name": "Yazami", "given_name": "Rachid", "orcid": "0000-0002-0085-5012", "clpid": "Yazami-R" }, { "family_name": "Gabrisch", "given_name": "Heike", "clpid": "Gabrisch-H" }, { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Single walled carbon nanotubes (SWNTs) were reacted with molten lithium at 220 \u00b0C for two weeks. This induced dramatic changes in their structure as shown by x-ray and electron diffractometry and Raman spectroscopy. A significant fraction of the initial SWNTs transformed into flat nanostrips having intercalated lithium in between them. Lithium forms a superlattice commensurate with that of the graphitelike nanostrips with [square root of]7\u00d7[square root of]3 in-plane distribution. This new structure corresponds to the LiC10 composition.", "doi": "10.1063/1.1427704", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "2001-12-15", "series_number": "23", "volume": "115", "issue": "23", "pages": "10585-10588" }, { "id": "authors:cagv1-e0295", "collection": "authors", "collection_id": "cagv1-e0295", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191008-100015006", "type": "article", "title": "Polarization Factors for ^(57)Fe M\u00f6ssbauer Diffractions from Polycrystals", "author": [ { "family_name": "Lin", "given_name": "J. Y. Y.", "orcid": "0000-0001-9233-0100", "clpid": "Lin-Jiao-Y-Y" }, { "family_name": "Kriplani", "given_name": "U.", "clpid": "Kriplani-U" }, { "family_name": "Regehr", "given_name": "M.", "clpid": "Regehr-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The intensities of M\u00f6ssbauer diffractions are calculated for polycrystalline samples in the kinematical limit, including interference with X-ray electronic scattering. The orientation distribution of hyperfine magnetic fields is expanded in spherical harmonics, providing a general expression for the polarization factor for magnetic dipole radiation. A comparison is made to experimental data reported recently.", "doi": "10.1023/a:1020547126883", "issn": "0304-3843", "publisher": "Springer Nature", "publication": "Hyperfine Interactions", "publication_date": "2001-11", "series_number": "3/8", "volume": "136/137", "issue": "3/8", "pages": "663-672" }, { "id": "authors:08wr7-qad30", "collection": "authors", "collection_id": "08wr7-qad30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CHEjap01", "type": "article", "title": "Nanocrystalline iron at high pressure", "author": [ { "family_name": "Chen", "given_name": "B.", "clpid": "Chen-B" }, { "family_name": "Penwell", "given_name": "D.", "clpid": "Penwell-D" }, { "family_name": "Kruger", "given_name": "M. B.", "clpid": "Kruger-M-B" }, { "family_name": "Yue", "given_name": "A. F.", "clpid": "Yue-Alan-F" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "X-ray diffraction measurements were performed on nanocrystalline iron up to 46 GPa. For nanocrystalline epsilon-Fe, analysis of lattice parameter data provides a bulk modulus, K, of 179\u00b18 GPa and a pressure derivative of the bulk modulus, K[prime], of 3.6\u00b10.7, similar to the large-grained control sample. The extrapolated zero-pressure unit cell volume of nanocrystalline epsilon-Fe is 22.9\u00b10.2 \u00c5^3, compared to 22.3\u00b10.2 \u00c5^3 for large-grained epsilon-Fe. No significant grain growth was observed to occur under pressure.", "doi": "10.1063/1.1357780", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2001-05-01", "series_number": "9", "volume": "89", "issue": "9", "pages": "4794-4796" }, { "id": "authors:qveys-yj638", "collection": "authors", "collection_id": "qveys-yj638", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MANprl01", "type": "article", "title": "Large harmonic softening of the phonon density of states of uranium", "author": [ { "family_name": "Manley", "given_name": "M. E.", "orcid": "0000-0003-4053-9986", "clpid": "Manley-M-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "McQueeney", "given_name": "R. J.", "clpid": "McQueeney-R-J" }, { "family_name": "Brown", "given_name": "C. M.", "clpid": "Brown-C-M" }, { "family_name": "Hults", "given_name": "W. L.", "clpid": "Hults-W-L" }, { "family_name": "Smith", "given_name": "J. L.", "clpid": "Smith-J-L" }, { "family_name": "Thoma", "given_name": "D. J.", "clpid": "Thoma-D-J" }, { "family_name": "Osborn", "given_name": "R.", "clpid": "Osborn-R" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" } ], "abstract": "Phonon density-of-states curves were obtained from inelastic neutron scattering spectra from the three crystalline phases of uranium at temperatures from 50 to 1213 K. The alpha -phase showed an unusually large thermal softening of phonon frequencies. Analysis of the vibrational power spectrum showed that this phonon softening originates with the softening of a harmonic solid, as opposed to vibrations in anharmonic potentials. It follows that thermal excitations of electronic states are more significant thermodynamically than are the classical volume effects. For the alpha-beta and beta-gamma phase transitions, vibrational and electronic entropies were comparable.", "doi": "10.1103/PhysRevLett.86.3076", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2001-04-02", "series_number": "14", "volume": "86", "issue": "14", "pages": "3076-3079" }, { "id": "authors:n9zeg-nnn67", "collection": "authors", "collection_id": "n9zeg-nnn67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PASprb01", "type": "article", "title": "Thermal vacancy formation and D03 ordering in nanocrystalline intermetallic (Fe3Si)95Nb5", "author": [ { "family_name": "Pasquini", "given_name": "L.", "clpid": "Pasquini-L" }, { "family_name": "Rempel", "given_name": "A. A.", "clpid": "Rempel-A-A" }, { "family_name": "W\u00fcrschum", "given_name": "R.", "clpid": "W\u00fcrschum-R" }, { "family_name": "Reimann", "given_name": "K.", "clpid": "Reimann-K" }, { "family_name": "M\u00fcller", "given_name": "M. A.", "clpid": "M\u00fcller-M-A" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Schaefer", "given_name": "H.-E.", "clpid": "Schaefer-H-E" } ], "abstract": "The correlation between thermal vacancy characteristics and D0(3) ordering in ball-milled nanocrystalline (Fe3Si)(95)Nb-5 was studied by combined measurements of x-ray diffraction and positron annihilation. Structural stabilization due to grain boundary segregation of Nb enables high-temperature positron lifetime measurements up to 1023 K from which vacancy formation parameters identical to those in single-crystalline D0(3) Fe3Si are deduced. Measurements of coincidence Doppler broadening show that prior to the onset of thermal defect formation in the nanocrystallites, positrons are annihilated in Nb-enriched grain boundaries. The D0(3) ordering of the initially disordered Fe3Si nanocrystallites is discussed on the basis of the thermal vacancy characteristics and self-diffusion behavior.", "doi": "10.1103/PhysRevB.63.134114", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2001-04-01", "series_number": "13", "volume": "63", "issue": "13", "pages": "Art. No. 134114" }, { "id": "authors:cwpr4-f7w78", "collection": "authors", "collection_id": "cwpr4-f7w78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YEYapl00", "type": "article", "title": "Hydrogen adsorption and phase transitions in fullerite", "author": [ { "family_name": "Ye", "given_name": "Y.", "clpid": "Ye-Y" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Vajo", "given_name": "J. J.", "orcid": "0000-0002-6271-4899", "clpid": "Vajo-J-J" }, { "family_name": "Zinck", "given_name": "J. J.", "clpid": "Zinck-J-J" } ], "abstract": "Hydrogen desorption and adsorption properties of the fullerene materials C60, C70, and fullerite (a mixture of C60 and C70) were measured volumetrically using a Sievert's apparatus. Over several cycles of isotherm measurements at 77 K, the hydrogen storage capacities of one of the fullerite samples increased from an initial value of 0.4 wt % for the first cycle to a capacity of 4.4 wt % for the fourth cycle. Correspondingly, the surface area of this sample increased from 0.9 to 11 m^2/g, and there were changes in its x-ray powder diffraction pattern. In comparison, two other fullerite samples, prepared by a different procedure showed no such behavior. Pure C60 and pure C70 were also cycled and exhibited small and constant capacities of 0.7 and 0.33 wt %, respectively, as a function of number of cycles. The enhanced storage capacity of fullerite material is tentatively attributed to the presence of C60 oxide.", "doi": "10.1063/1.1312857", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "2000-10-02", "series_number": "14", "volume": "77", "issue": "14", "pages": "2171-2173" }, { "id": "authors:8f0qp-s5q96", "collection": "authors", "collection_id": "8f0qp-s5q96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HIGapl00", "type": "article", "title": "Electron energy-loss spectrometry on lithiated graphite", "author": [ { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Rez", "given_name": "P.", "clpid": "Rez-P" } ], "abstract": "Transmission electron energy-loss spectrometry was used to investigate the electronic states of metallic Li and LiC6, which is the Li-intercalated graphite used in Li-ion batteries. The Li K edges of metallic Li and LiC6 were nearly identical, and the C K edges were only weakly affected by the presence of Li. These results suggest only a small charge transfer from Li to C in LiC6, contrary to prior results from surface spectra obtained by x-ray photoelectron spectroscopy. Effects of radiation damage and sample oxidation in the transmission electron microscopy are also reported.", "doi": "10.1063/1.126936", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "2000-07-10", "series_number": "2", "volume": "77", "issue": "2", "pages": "238-240" }, { "id": "authors:2esbd-9nv48", "collection": "authors", "collection_id": "2esbd-9nv48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb00", "type": "article", "title": "Atom clusters and vibrational excitations in chemically-disordered Pt357Fe", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Stephens", "given_name": "T. A.", "clpid": "Stephens-T-A" }, { "family_name": "Alp", "given_name": "E. E.", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Hu", "given_name": "M. Y.", "orcid": "0000-0002-3718-7169", "clpid": "Hu-Michael-Y" }, { "family_name": "Sutter", "given_name": "J. P.", "clpid": "Sutter-J-P" }, { "family_name": "Toellner", "given_name": "T. S.", "clpid": "Toellner-T-S" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" } ], "abstract": "Inelastic nuclear resonant scattering spectra of Fe-57 atoms were measured on crystalline alloys of Pt3Fe-57 that were chemically disordered, partially ordered, and L1(2) ordered. Phonon partial density of states curves for Fe-57 were obtained from these spectra. Upon disordering, about 10% of the spectral intensity underwent a distinct shift from 25 to 19 meV. This change in optical modes accounted for most of the change of the vibrational entropy of disordering contributed by Fe atoms, which was (+0.10 +/- 0.03) k(B) (Fe atom)(-1). Prospects for parametrizing the vibrational entropy with low-order cluster variables were assessed. To calculate the difference in vibrational entropy of the disordered and ordered alloys, the clusters must be large enough to account for the abundances of several of the atom configurations of the first-nearest-neighbor shell about the Fe-57 atoms.", "doi": "10.1103/PhysRevB.61.14517", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "2000-06-01", "series_number": "21", "volume": "61", "issue": "21", "pages": "14517-14522" }, { "id": "authors:bv5vd-pad67", "collection": "authors", "collection_id": "bv5vd-pad67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GRAjap00", "type": "article", "title": "Magnetomechanical effects in textured polycrystalline Tb76Dy24", "author": [ { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Good", "given_name": "N.", "clpid": "Good-N" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Dooley", "given_name": "J.", "clpid": "Dooley-J" }, { "family_name": "Chave", "given_name": "R.", "clpid": "Chave-R" } ], "abstract": "Uniaxial stress-strain measurements were performed on polycrystalline Tb76Dy24 alloys which exhibit \"giant magnetostriction\" at cryogenic temperatures. The Young's moduli were reduced by up to a factor of five at 77 K, in comparison to their values at 300 K. We attribute this reduction to a mechanical compliance from domain rotation. Large mechanical hysteresis is also found in nominally elastic stress-strain curves measured below the Curie temperature. Hysteretic curves from 0 to 25 MPa demonstrate up to 19% dissipation of the applied mechanical energy. The anisotropy of thermal expansion was also measured and used as a parameter for the degree of crystallographic texture. This anisotropy was correlated to bulk magnetostriction and to mechanical hysteresis.", "doi": "10.1063/1.372525", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2000-05-01", "series_number": "9", "volume": "87", "issue": "9", "pages": "5795-5798" }, { "id": "authors:t8ta3-mcp15", "collection": "authors", "collection_id": "t8ta3-mcp15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111208-070606920", "type": "article", "title": "A ^(119)Sn M\u00f6ssbauer Spectrometry Study of Li-SnO Anode\n Materials for Li-Ion Cells", "author": [ { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Delcroix", "given_name": "P.", "clpid": "Delcroix-P" }, { "family_name": "Le Ca\u00ebr", "given_name": "G.", "clpid": "Le-Ca\u00ebr-G" }, { "family_name": "Huang", "given_name": "C.-K.", "clpid": "Huang-C-K" }, { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Anodes of SnO were charged reversibly with Li to capacities greater than 600 mAh/g, The anode materials were characterized by 119Sn M\u00f6ssbauer spectrometry at 11 and 300 K, and by X-ray diffractometry at 300 K. Trends in the valence of Sn were as expected when the Sn oxides are reduced in the presence of Li. At low Li capacities the SnO is reduced to small particles of \u03b2-Sn, and with increasing Li capacity an alloy of Li_(22)Sn_5 is formed. Although the Li_(22)Sn_5 develops over a range of Li concentrations in the anode material, the Li_(22)Sn_5 that forms at low Li insertions is not typical of bulk Li_(22)Sn_5 in either its structural or electrochemical properties. The recoil-free fraction of the Sn oxide (and perhaps the metallic Sn) in the anode materials showed an anomalously large temperature dependence. This is indicative of nanoparticles or a severely defective structure. We monitored the changes in the Li-SnO and Li-Sn materials during atmospheric exposure over times up to 2 months. This oxidation process of Sn was very much the reverse of the Sn reduction during the Li insertion, although it occurred over a much longer time scale. We also report the temperature dependencies of recoil-free fractions for standard samples of \u03b2-Sn, SnO_2, and the alloy Li_(22)Sn_5.", "doi": "10.1149/1.1493855", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2000-01", "series_number": "1", "volume": "147", "issue": "1", "pages": "1-8" }, { "id": "authors:skk31-r2m60", "collection": "authors", "collection_id": "skk31-r2m60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200205-153152101", "type": "article", "title": "Grain boundaries of nanocrystalline materials \u2013 their widths, compositions, and internal structures", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Frase", "given_name": "H. N.", "clpid": "Frase-H-N" } ], "abstract": "Nanocrystalline materials contain many atoms at and near grain boundaries. Sufficient numbers of M\u00f6ssbauer probe atoms can be situated in grain boundary environments to make a clear contribution to the measured M\u00f6ssbauer spectrum. Three types of measurements on nanocrystalline materials are reported here, all using M\u00f6ssbauer spectrometry in conjunction with X-ray diffractometry, transmission electron microscopy, or small angle neutron scattering. By measuring the fraction of atoms contributing to the grain boundary component in a M\u00f6ssbauer spectrum, and by knowing the grain size of the material, it is possible to deduce the average width of grain boundaries in metallic alloys. It is found that these widths are approximately 0.5 nm for fcc alloys and slightly larger than 1.0 nm for bcc alloys.\nChemical segregation to grain boundaries can be measured by M\u00f6ssbauer spectrometry, especially in conjunction with small angle neutron scattering. Such measurements on Fe-Cu and Fe\u2083Si-Nb were used to study how nanocrystalline materials could be stabilized against grain growth by the segregation of Cu and Nb to grain boundaries. The segregation of Cu to grain boundaries did not stabilize the Fe-Cu alloys against grain growth, since the grain boundaries were found to widen and accept more Cu atoms during annealing. The Nb additions to Fe\u2083Si did suppress grain growth, perhaps because of the low mobility of Nb atoms, but also perhaps because Nb atoms altered the chemical ordering in the alloy.\nThe internal structure of grain boundaries in nanocrystalline materials prepared by high-energy ball milling is found to be unstable against internal relaxations at low temperatures. The M\u00f6ssbauer spectra of the nanocrystalline samples showed changes in the hyperfine fields attributable to movements of grain boundary atoms. In conjunction with SANS measurements, the changes in grain boundary structure induced by cryogenic exposure and annealing at low temperature were found to be somewhat different. Both were consistent with a sharper density gradient between the crystalline region and the grain boundary region.", "doi": "10.1023/a:1011056927880", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "2000-01", "series_number": "1-4", "volume": "130", "issue": "1-4", "pages": "81-108" }, { "id": "authors:83dve-2vq47", "collection": "authors", "collection_id": "83dve-2vq47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120109-142746392", "type": "article", "title": "Irreversible Capacities of Graphite in Low-Temperature\n Electrolytes for Lithium-Ion Batteries", "author": [ { "family_name": "Smart", "given_name": "M. C.", "clpid": "Smart-M-C" }, { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Surampudi", "given_name": "S.", "clpid": "Surampudi-S" }, { "family_name": "Wang", "given_name": "Y.", "clpid": "Wang-Y" }, { "family_name": "Zhang", "given_name": "X.", "clpid": "Zhang-X" }, { "family_name": "Greenbaum", "given_name": "S. G.", "clpid": "Greenbaum-S-G" }, { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Carbonaceous anode materials in lithium-ion rechargeable cells exhibit irreversible capacity, mainly due to reaction of lithium during the formation of passive surface films. The stability and kinetics of lithium intercalation into the carbon anodes are determined by these films. The nature, thickness, and morphology of these films are in turn affected by the electrolyte components, primarily the solvent constituents. In this work, the films formed on graphite anodes in low-temperature electrolytes, i.e., solutions with different mixtures of alkyl carbonates and low-viscosity solvent additives, are examined using electrochemical impedance spectroscopy (EIS) and solid-state ^(7)Li nuclear magnetic resonance techniques. In addition, other ex situ studies such as X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy were carried out on the graphite anodes to understand their microstructures.", "doi": "10.1149/1.1392577", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "1999-11", "series_number": "11", "volume": "146", "issue": "11", "pages": "3963-3969" }, { "id": "authors:3t0pm-z3a48", "collection": "authors", "collection_id": "3t0pm-z3a48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ROBprb99", "type": "article", "title": "Phonon contributions to the entropies of hP24 and fcc Co3V", "author": [ { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Frase", "given_name": "H. N.", "clpid": "Frase-H-N" } ], "abstract": "Inelastic neutron-scattering spectra and neutron-diffraction patterns were measured on the alloy Co3V at temperatures from 1073-1513 K, where the hP24 (ordered hexagonal) and fee structures are the equilibrium states of the alloy. Phonon density of states (DOS) curves were calculated from the inelastic-scattering spectra, allowing estimates of the vibrational entropy in the harmonic and quasiharmonic approximations. The vibrational entropy of the hP24-fcc phase transition at 1323 K was found to be 0.07k(B)/atom. The anharmonic contributions to the entropy over a temperature range of 100 K were comparable to the vibrational entropy of this phase transition. The anharmonic softening of the phonon DOS was only slightly larger for the hP24 than the fee phase, however, so the anharmonic effects contribute only slightly to the difference in entropy of the two phases. The simple Gruneisen approximation was inadequate for predicting the thermal softening of the phonon DOS.", "doi": "10.1103/PhysRevB.60.9329", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1999-10-01", "series_number": "13", "volume": "60", "issue": "13", "pages": "9329-9334" }, { "id": "authors:5z6ja-dwg73", "collection": "authors", "collection_id": "5z6ja-dwg73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BOGprb99", "type": "article", "title": "Vibrational entropy of L12 Cu3Au measured by inelastic neutron scattering", "author": [ { "family_name": "Bogdanoff", "given_name": "P. D.", "clpid": "Bogdanoff-P-D" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Rosenkranz", "given_name": "S.", "clpid": "Rosenkranz-S" } ], "abstract": "The phonon density of states of elemental Au, Cu, and Cu3Au with L12 chemical order were measured by inelastic neutron scattering and used to calculate the vibrational entropy of formation of the ordered compound from the elemental metals. A vibrational entropy of formation of (0.06\u00b10.03) kB/atom at 300 K was obtained, with the vibrational entropy of the ordered alloy being larger than that of the elemental metals. The phonon DOS of the disordered Cu3Au was simulated by adding the phonon DOS curves of fcc Cu, L12 Cu3Au, and fcc Au to match the numbers of first-nearest-neighbor pairs in a disordered alloy. The vibrational entropy obtained with this simulated DOS disagrees with calorimetric data and theoretical estimates, indicating that the phonon DOS of disordered Cu3Au depends on chemical order at spatial lengths larger than is set by first-nearest-neighbor pairs.", "doi": "10.1103/PhysRevB.60.3976", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1999-08-01", "series_number": "6", "volume": "60", "issue": "6", "pages": "3976-3981" }, { "id": "authors:qe6s4-z1654", "collection": "authors", "collection_id": "qe6s4-z1654", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FRAjap99", "type": "article", "title": "A small angle neutron scattering and M\u00f6ssbauer spectrometry study of magnetic structures in nanocrystalline Ni3Fe", "author": [ { "family_name": "Frase", "given_name": "H. N.", "clpid": "Frase-H-N" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Spooner", "given_name": "S.", "clpid": "Spooner-S" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" } ], "abstract": "Results are reported from small angle neutron scattering and M\u00f6ssbauer spectrometry measurements on nanocrystalline Ni3Fe. The nanocrystalline materials were prepared by mechanical attrition and studied in the as-milled state, after annealing at 265 \u00b0C to relieve internal stress, and after annealing 600 \u00b0C to prepare a control sample comprising large crystals. The small angle neutron scattering (SANS) measurements were performed for a range of applied magnetic fields. Small differences were found in how the different samples reached magnetic saturation. From the SANS data obtained at magnetic saturation, we found little difference in the nuclear scattering of the as-milled material and the material annealed at 265 \u00b0C. Reductions in nuclear scattering and magnetic scattering were observed for the control sample, and this was interpreted as grain growth. The material annealed at 265 \u00b0C also showed a reduction in magnetic SANS compared to the as-milled material. This was interpreted as an increase in magnetic moments of atoms at the grain boundaries after a low temperature annealing. Both M\u00f6ssbauer spectroscopy and small angle neutron scattering showed an increase in the grain boundary magnetic moments after the 265 \u00b0C annealing (0.2 and 0.4\u00b5B/atom, respectively), even though there was little change in the grain boundary atomic density.", "doi": "10.1063/1.370517", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1999-05-15", "series_number": "10", "volume": "85", "issue": "10", "pages": "7097-8004" }, { "id": "authors:799gc-eca88", "collection": "authors", "collection_id": "799gc-eca88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YEYapl99", "type": "article", "title": "Hydrogen adsorption and cohesive energy of single-walled carbon nanotubes", "author": [ { "family_name": "Ye", "given_name": "Y.", "clpid": "Ye-Y" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Witham", "given_name": "C.", "clpid": "Witham-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Liu", "given_name": "J.", "clpid": "Liu-J" }, { "family_name": "Rinzler", "given_name": "A. G.", "clpid": "Rinzler-A-G" }, { "family_name": "Colbert", "given_name": "D.", "clpid": "Colbert-D" }, { "family_name": "Smith", "given_name": "K. A.", "clpid": "Smith-K-A" }, { "family_name": "Smalley", "given_name": "R. E.", "clpid": "Smalley-R-E" } ], "abstract": "Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes (SWNT) was found to exceed 8 wt.%, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occurs where there is a separation of the individual SWNTs, and hydrogen is physisorbed on their exposed surfaces. The pressure of this phase transition provides a tube-tube cohesive energy for much of the material of 5 meV/C atom. This small cohesive energy is affected strongly by the quality of crystalline order in the ropes.", "doi": "10.1063/1.123833", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "1999-04-19", "series_number": "16", "volume": "74", "issue": "16", "pages": "2307-2309" }, { "id": "authors:dt76n-15n62", "collection": "authors", "collection_id": "dt76n-15n62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DOOjap99", "type": "article", "title": "Magnetostriction of single crystal and polycrystalline Tb0.60Dy0.40 at cryogenic temperatures", "author": [ { "family_name": "Dooley", "given_name": "J. A,", "clpid": "Dooley-J-A" }, { "family_name": "Lindensmith", "given_name": "C. A.", "clpid": "Lindensmith-C-A" }, { "family_name": "Chave", "given_name": "R. G.", "clpid": "Chave-R-G" }, { "family_name": "Good", "given_name": "N.", "clpid": "Good-N" }, { "family_name": "Graetz", "given_name": "J.", "clpid": "Graetz-J" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "At cryogenic temperatures, single crystals of TbDy alloys exhibit giant magnetostrictions of nearly 9000 ppm, making these materials promising for engineering service in cryogenic actuators, valves, and positioners. The preparation of single crystals is difficult and costly. Preliminary results on the magnetostriction of textured polycrystalline materials are presented here. For instance, polycrystalline Tb0.60Dy0.40, plane-rolled (one direction of applied stress) to induce crystallographic texture, has shown magnetostrictions at 77 K of 3000 ppm for an applied field of 4.5 kOe and an applied load of 23 MPa, or 48% that of a single crystal under similar conditions. Comparisons are presented between the magnetostrictive response of plane- and form-rolled (two orthogonal directions of applied stress) polycrystalline Tb0.60Dy0.40 at 10 and 77 K. It is reported that at 10 K plane-rolled Tb0.60Dy0.40 exhibits 1600 ppm magnetostriction at an applied field of 4.4 kOe with a minimal applied load of 0.28 MPa. An observed restoration of the initial unstrained state may be a useful feature of polycrystalline materials for engineering service. Finally it is reported that thermal expansion measurements provide a measure of crystallographic texture for comparison with the magnetostriction.", "doi": "10.1063/1.370128", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1999-04-15", "series_number": "8", "volume": "85", "issue": "8", "pages": "6256-6258" }, { "id": "authors:4dk0z-5cs52", "collection": "authors", "collection_id": "4dk0z-5cs52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:AHNapl99", "type": "article", "title": "Hydrogen desorption and adsorption measurements on graphite nanofibers", "author": [ { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Ye", "given_name": "Y.", "clpid": "Ye-Y" }, { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Witham", "given_name": "C.", "clpid": "Witham-C" }, { "family_name": "Bowman", "given_name": "R. C.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Graphite nanofibers were synthesized and their hydrogen desorption and adsorption properties are reported for 77 and 300 K. Catalysts were made by several different methods including chemical routes, mechanical alloying, and gas condensation. The nanofibers were grown by passing ethylene and H2 gases over the catalysts at 600 \u00b0C. Hydrogen desorption and adsorption were measured using a volumetric analysis Sieverts' apparatus, and the graphite nanofibers were characterized by transmission electron microscopy and Brunauer\u2013Emmett\u2013Teller surface area analysis. The absolute level of hydrogen desorption measured from these materials was typically less than the 0.01 H/C atom, comparable to other forms of carbon.", "doi": "10.1063/1.122755", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "1998-12-07", "series_number": "23", "volume": "73", "issue": "23", "pages": "3378-3380" }, { "id": "authors:wf17b-7ft75", "collection": "authors", "collection_id": "wf17b-7ft75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprl98", "type": "article", "title": "Local Chemical Environments and the Phonon Partial Densities of States of 57Fe in 57Fe3Al", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Stephens", "given_name": "T. A.", "clpid": "Stephens-T-A" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Toellner", "given_name": "T. S.", "clpid": "Toellner-T-S" }, { "family_name": "Alp", "given_name": "E. E.", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" } ], "abstract": "Inelastic nuclear resonant scattering spectra were measured on alloys of Fe3Al that were chemically disordered, partially ordered, and D03 ordered. The features in the phonon partial density of states of 57Fe were found to change systematically with chemical short-range order in the alloy. Changes in the phonon partial density of states were modeled successfully by assigning vibrational spectra to 57Fe atoms in different first-nearest-neighbor chemical environments.", "doi": "10.1103/PhysRevLett.80.3304", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1998-04-13", "series_number": "15", "volume": "80", "issue": "15", "pages": "3304-3307" }, { "id": "authors:9qn48-ywj23", "collection": "authors", "collection_id": "9qn48-ywj23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FRAprb98", "type": "article", "title": "Phonons in nanocrystalline Ni3Fe", "author": [ { "family_name": "Frase", "given_name": "H.", "clpid": "Frase-H-N" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" } ], "abstract": "Inelastic neutron-scattering spectra were measured to obtain the phonon density of states (DOS) of nanocrystalline fcc Ni3Fe. The materials were prepared by mechanical alloying, and were also subjected to heat treatments to alter their crystallite sizes and internal strains. In comparison to material with large crystallites, the nanocrystalline material shows two distinct differences in its phonon DOS. The nanocrystalline DOS was more than twice as large at energies below 15 meV. This increase was approximately proportional to the density of grain boundaries in the material. Second, features in the nanocrystalline DOS are broadened substantially. This broadening did not depend in a simple way on the crystallite size of the sample, suggesting that it has a different physical origin than the enhancement in phonon DOS at energies below 15 meV. A damped harmonic oscillator model for the phonons provides a quality factor Qu, as low as 7 for phonons in the nanocrystalline material. The difference in vibrational entropy of the bulk and nanocrystalline Ni3Fe was small, owing to competing changes in the nanocrystalline phonon DOS at low and high energies.", "doi": "10.1103/PhysRevB.57.898", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1998-01-01", "series_number": "2", "volume": "57", "issue": "2", "pages": "898-905" }, { "id": "authors:1193v-f0806", "collection": "authors", "collection_id": "1193v-f0806", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:RAVprb98", "type": "article", "title": "Free energy and vibrational entropy difference between ordered and disordered Ni3Al", "author": [ { "family_name": "Ravelo", "given_name": "R.", "clpid": "Ravelo-R" }, { "family_name": "Aguilar", "given_name": "J.", "orcid": "0000-0003-3184-0873", "clpid": "Aguilar-J" }, { "family_name": "Baskes", "given_name": "M.", "clpid": "Baskes-M" }, { "family_name": "Angelo", "given_name": "J. E.", "clpid": "Angelo-J-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Holian", "given_name": "Brad Lee", "clpid": "Holian-B-L" } ], "abstract": "We have calculated free energy and vibrational entropy differences in Ni3Al between its equilibrium ordered structure and a disordered fcc solid solution. The free energy and entropy differences were calculated using the method of adiabatic switching in a molecular-dynamics formalism. The path chosen for the free-energy calculations directly connects the disordered with the ordered state. The atomic interactions are described by embedded-atom-method potentials. We find that the vibrational entropy difference increases with temperature from 0.14kB/atom at 300 K to 0.22kB/atom at 1200 K. We have calculated the density of states (DOS) of the disordered phase from the Fourier transform of the velocity-velocity autocorrelation function. The disordered DOS looks more like a broadened version of the ordered DOS. Analysis of the partial density of states shows that the Al atoms vibrations are most affected by the compositional disorder. The phonon partial spectral intensities along the \u3008100\u3009 direction show that the vibrational spectrum of the disordered phase contains intensities at optical mode frequencies of the ordered alloy. We find that the volume difference between the ordered and disordered phases plays the most crucial role in the magnitude of the vibrational entropy difference. If the lattice constant of the two phases is set to the same value, the vibrational entropy difference decreases to zero.", "doi": "10.1103/PhysRevB.57.862", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1998-01-01", "series_number": "2", "volume": "57", "issue": "2", "pages": "862-869" }, { "id": "authors:bsr13-qw687", "collection": "authors", "collection_id": "bsr13-qw687", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WITjes97", "type": "article", "title": "Electrochemical Properties of LaNi5\u2013xGex Alloys in Ni-MH Batteries", "author": [ { "family_name": "Witham", "given_name": "C.", "clpid": "Witham-C" }, { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Bowman", "given_name": "R. C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" } ], "abstract": "Electrochemical studies were performed on LaNi5\u2013xGex metal hydride alloys with 0 <= x <= 0.5. We carried out single-electrode studies to understand the effects of the Ge substituent on the hydrogen absorption characteristics, the electrochemical capacity, and the electrochemical kinetics of hydrogen absorption and desorption. The electrochemical characteristics of the Ge-substituted alloys are compared to those of the Sn-substituted alloys reported earlier. LaNi5\u2013xGex alloys show compositional trends similar to LaNi5\u2013xSnx alloys, but unlike the Sn-substituted alloys, Ge-substituted alloys continue to exhibit facile kinetics for hydrogen absorption/desorption at high solute concentrations. Cycle lives of LaNi5\u2013xGex electrodes were measured in 300 mAh laboratory test cells and were found to be superior to the Sn-substituted LaNi5 and comparable to a Mm(Ni,Co,Mn,Al)5 alloy. The optimum Ge content for LaNi5\u2013xGex metal hydride alloys in alkaline rechargeable cells is in the range 0.4 <= x <= 0.5.", "doi": "10.1149/1.1838087", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "1997-11", "series_number": "11", "volume": "144", "issue": "11", "pages": "3758-3764" }, { "id": "authors:2nbns-wtk85", "collection": "authors", "collection_id": "2nbns-wtk85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprl97", "type": "article", "title": "Phonons in Nanocrystalline 57Fe", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Alp", "given_name": "E. E.", "orcid": "0000-0002-4803-8863", "clpid": "Alp-Esen-Ercan" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Toellner", "given_name": "T. S.", "clpid": "Toellner-T-S" } ], "abstract": "We measured the phonon density of states (DOS) of nanocrystalline Fe by resonant inelastic nuclear \u03b3-ray scattering. The nanophase material shows large distortions in its phonon DOS. We attribute the high energy distortion to lifetime broadening. A damped harmonic oscillator model for the phonons provides a low quality factor, Qu, averaging about 5, but the longitudinal modes may have been broadened most. The nanocrystalline Fe also shows an enhancement in its phonon DOS at energies below 15 meV. The difference in vibrational entropy of the bulk and nanocrystalline Fe was small, owing to competing changes in the nanocrystalline phonon DOS at low and high energies.", "doi": "10.1103/PhysRevLett.79.937", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1997-08-04", "series_number": "5", "volume": "79", "issue": "5", "pages": "937-940" }, { "id": "authors:9nfnf-e9f26", "collection": "authors", "collection_id": "9nfnf-e9f26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BIRprb97", "type": "article", "title": "Magnetic properties of bcc Fe-Pd extended solid solutions", "author": [ { "family_name": "Birsan", "given_name": "M.", "clpid": "Birsan-M" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Anthony", "given_name": "L.", "clpid": "Anthony-L" } ], "abstract": "Supersaturated Fe-Pd solid solutions were prepared by mechanical alloying. X-ray diffractometry showed that the as-milled alloys were bcc from 0\u201326 at. % Pd. Saturation magnetization measurements and M\u00f6ssbauer spectrometry measurements were performed on these powders. Consistent interpretations of both sets of measurements were possible if the magnetic moment at the Pd atom was 0.35\u03bcB and constant, and if the magnetic moments at Fe atoms were enhanced by neighboring Pd atoms in a way similar to the effects of Ni.", "doi": "10.1103/PhysRevB.55.11502", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1997-05-01", "series_number": "17", "volume": "55", "issue": "17", "pages": "11502-11506" }, { "id": "authors:5a990-13e31", "collection": "authors", "collection_id": "5a990-13e31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NAGprb97", "type": "article", "title": "Vibrational entropy and microstructural effects on the thermodynamics of partially disordered and ordered Ni3V", "author": [ { "family_name": "Nagel", "given_name": "L. J.", "clpid": "Nagel-L-J" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" }, { "family_name": "Spooner", "given_name": "S.", "clpid": "Spooner-S" } ], "abstract": "Samples of Ni3V were prepared with two microstructures: (1) with equilibrium D022 order, and (2) with partial disorder (having a large D022 chemical order parameter, but without the tetragonality of the unit cell). For both materials, we measured the difference in their heat capacities from 60 to 325 K, inelastic neutron-scattering spectra at four values of Q at 11 and at 300 K, and Young's moduli and coefficients of thermal expansion. The difference in heat capacity at low temperatures was consistent with a harmonic model using the phonon density of states (DOS) curves determined from the inelastic neutron-scattering spectra. In contrast, at temperatures greater than 160 K the difference in heat capacity did not approach zero, as expected of harmonic behavior. The temperature dependence of the phonon DOS can be used to approximately account for the anharmonic contributions to the differential heat capacity. We also argue that some of the anharmonic behavior should originate with a microstructural contribution to the heat capacity involving anisotropic thermal contractions of the D022 structure. We estimate the difference in vibrational entropy between partially disordered and ordered Ni3V to be Spdis -Sord =(+0.038\u00b10.015)kB /atom at 300 K.", "doi": "10.1103/PhysRevB.55.2903", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1997-02-01", "series_number": "5", "volume": "55", "issue": "5", "pages": "2903-2911" }, { "id": "authors:489h2-njh30", "collection": "authors", "collection_id": "489h2-njh30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:STEprl97", "type": "article", "title": "Chemical Environment Selectivity in M\u00f6ssbauer Diffraction from 57Fe3Al", "author": [ { "family_name": "Stephens", "given_name": "T. A.", "clpid": "Stephens-T-A" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "M\u00f6ssbauer diffraction was used to measure different autocorrelation functions for 57Fe atoms in different chemical environments. The sample was polycrystalline 57Fe3Al with the ordered DO3 structure. Diffraction peaks from a fcc structure with a doubled unit cell were detected when the incident radiation was tuned to the M\u00f6ssbauer resonance of the Wyckoff 4(b) Fe site, but not for tuning to the 8(c) site, thereby distinguishing the spatial arrangements of these two Fe sites.", "doi": "10.1103/PhysRevLett.78.366", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1997-01-13", "series_number": "2", "volume": "78", "issue": "2", "pages": "366-369" }, { "id": "authors:xc77m-vmv17", "collection": "authors", "collection_id": "xc77m-vmv17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120202-133457974", "type": "article", "title": "Electrochemical Evaluation of LaNi_(5\u2013x)Ge_x Metal Hydride Alloys", "author": [ { "family_name": "Witham", "given_name": "C.", "clpid": "Witham-C" }, { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Bowman", "given_name": "R. C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We report a detailed evaluation of Ge-substituted LaNi_5 for electrochemical application as a negative electrode in alkaline rechargeable cells. Alloys with small substitutions of Ge for Ni show operating pressures, chargeability, cyclic lifetime, and kinetics for hydrogen absorption and desorption all superior to those found in many other substituted LaNi_5 alloys. These improved properties were achieved with a minimal reduction in hydrogen storage capacity.", "doi": "10.1149/1.1837088", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "1996-09", "series_number": "9", "volume": "143", "issue": "9", "pages": "L205-L208" }, { "id": "authors:e9cy1-1cn12", "collection": "authors", "collection_id": "e9cy1-1cn12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:RATjes96", "type": "article", "title": "Electrochemical Studies on LaNi5\u2013xSnx Metal Hydride Alloys", "author": [ { "family_name": "Ratnakumar", "given_name": "B. V.", "clpid": "Ratnakumar-B-V" }, { "family_name": "Witham", "given_name": "C.", "clpid": "Witham-C" }, { "family_name": "Bowman", "given_name": "R. C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Hightower", "given_name": "A.", "clpid": "Hightower-Adrian" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Electrochemical studies were performed on LaNi5\u2013xSnx with 0 <= x <= 0.5. We measured the effect of the Sn substituent on the kinetics of charge-transfer and diffusion during hydrogen absorption and desorption, and the cyclic lifetimes of LaNi5\u2013-xSnx electrodes in 250 mAh laboratory test cells. We report beneficial effects of making small substitutions of Sn for Ni in LaNi5 on the performance of the metal hydride alloy anode in terms of cyclic lifetime, capacity, and kinetics. The optimal concentration of Sn in LaNi5\u2013xSnx alloys for negative electrodes in alkaline rechargeable secondary cells was found to lie in the range 0.25 <= x <= 0.3.", "doi": "10.1149/1.1837050", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "1996-08", "series_number": "8", "volume": "143", "issue": "8", "pages": "2578-2584" }, { "id": "authors:vc79p-bqj26", "collection": "authors", "collection_id": "vc79p-bqj26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULjap96", "type": "article", "title": "Phonon density of states of nanocrystalline Fe prepared by high-energy ball milling", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" }, { "family_name": "Stephens", "given_name": "T. A.", "clpid": "Stephens-T-A" }, { "family_name": "Nagel", "given_name": "L. J.", "clpid": "Nagel-L-J" }, { "family_name": "Spooner", "given_name": "S.", "clpid": "Spooner-S" } ], "abstract": "We performed inelastic neutron scattering measurements on nanophase Fe powders prepared by high-energy ball milling. Neutron energy loss spectra were measured for two states of the material: (1) as milled, when the material had a characteristic nanocrystallite size of 12 nm; and (2) annealed, when the material had a characteristic crystallite size of 28 nm. The longitudinal peak in the phonon density of states (DOS) of the nanophase Fe was broadened, compared to that of the annealed material. We attribute this broadening to short phonon lifetimes in nanocrystals. The nanophase material also showed an enhanced density of states at low energies below 15 meV, which may indicate the presence of intercrystallite vibrations. These differences in phonon DOS should have only a small effect on the difference in vibrational entropy of nanocrystalline and larger-grained Fe.", "doi": "10.1063/1.362543", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1996-06-01", "series_number": "11", "volume": "79", "issue": "11", "pages": "8318-8322" }, { "id": "authors:5mcw9-0r204", "collection": "authors", "collection_id": "5mcw9-0r204", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HONjap96", "type": "article", "title": "Two-phase coexistence in Fe\u2013Ni alloys synthesized by ball milling", "author": [ { "family_name": "Hong", "given_name": "L. B.", "clpid": "Hong-L-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We used mechanical alloying with a Spex 8000 mixer/mill to synthesize a series of Fe100\u2013xNix alloys from x=0 to x=49. The Spex mill was modified so that it could also operate at a reduced milling intensity, and we compared the alloys synthesized after long times with the normal and reduced milling intensities. X-ray diffractometry and M\u00f6ssbauer spectrometry were used to measure the volume fractions of the bcc and fcc phases in the alloys, and to determine the chemical compositions of the individual phases. We found that the composition ranges of the bcc and fcc single phase regions were extended well beyond their equilibrium ranges. At the higher milling intensity, we found that the bcc phase was destabilized with respect to the fcc phase, and the two-phase region shifted to lower Ni concentrations. For those alloys with coexisting bcc and fcc phases, we present evidence that the chemical compositions of the two phases are nearly the same. We explain the destabilization of the bcc with milling intensity as originating with a higher defect density in the bcc alloys than in the fcc alloys. We argue that this defect density is not homogeneous throughout the alloy, however, and the distribution of defect enthalpies can explain the two-phase coexistence in the as-milled alloys.", "doi": "10.1063/1.361821", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1996-04-15", "series_number": "8", "volume": "79", "issue": "8", "pages": "3946-3955" }, { "id": "authors:0nn73-6h718", "collection": "authors", "collection_id": "0nn73-6h718", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HONprb95b", "type": "article", "title": "Phase diagrams of bcc alloys at low temperatures with ballistic atom movements", "author": [ { "family_name": "Hong", "given_name": "L. B.", "clpid": "Hong-L-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Kinetic Monte Carlo simulations were used to determine the steady states of equiatomic bcc alloys with first- and second-nearest-neighbor (1NN and 2NN) effective pair interactions. Atom movements occurred with a vacancy mechanism, and were of two types: thermal and ballistic. The phase diagram in the space spanned by the 1NN and 2NN interaction strengths was determined for thermal atom movements alone, and with some ballistic atom movements. With increasing temperature, the region of B32 phase receded against the adjacent regions of B2 order and unmixed states. With some ballistic atom movements, however, the region of B32 order encroached on the adjacent regions of B2 order and unmixed state. The shifts in phase boundaries are attributed to differences in how the internal energies of the different phases are affected by ballistic atom movements. Local fluctuations in the internal energy density in the presence of ballistic atom movements caused two-phase regions in the phase diagram.", "doi": "10.1103/PhysRevB.52.6230", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1995-09-01", "series_number": "9", "volume": "52", "issue": "9", "pages": "6230-6237" }, { "id": "authors:t8g17-2xz38", "collection": "authors", "collection_id": "t8g17-2xz38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb95b", "type": "article", "title": "Phonon modes and vibrational entropy of mixing in Fe-Cr", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Anthony", "given_name": "L.", "clpid": "Anthony-L" }, { "family_name": "Robertson", "given_name": "J. L.", "clpid": "Robertson-J-L" }, { "family_name": "Nicklow", "given_name": "R. M.", "clpid": "Nicklow-R-M" }, { "family_name": "Spooner", "given_name": "S.", "clpid": "Spooner-S" }, { "family_name": "Mostoller", "given_name": "M.", "clpid": "Mostoller-M" } ], "abstract": "Results from neutron inelastic-scattering experiments on Fe, Cr, and three bcc Fe-Cr alloys were analyzed with a Born\u2013von K\u00e1rm\u00e1n model to obtain phonon density-of-states (DOS) curves. We compared the phonon DOS of the bcc Fe-Cr alloys to the composite phonon DOS from appropriate fractions of the phonon DOS of the pure metals Fe and Cr. In the high-temperature limit, we obtained the vibrational entropy of mixing of Fe and Cr to be 0.141, 0.201, and 0.214 kB/atom for alloys of Fe70Cr30,Fe53Cr47, and Fe30Cr70, respectively, with the disordered solid solution having the larger vibrational entropy. Some expected effects of vibrational entropy on the chemical unmixing transformation in Fe-Cr are discussed.", "doi": "10.1103/PhysRevB.52.3280", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1995-08-01", "series_number": "5", "volume": "52", "issue": "5", "pages": "3280-3285" }, { "id": "authors:w31m6-v2688", "collection": "authors", "collection_id": "w31m6-v2688", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb95a", "type": "article", "title": "Phonon densities of states and vibrational entropies of ordered and disordered Ni3Al", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Anthony", "given_name": "L.", "clpid": "Anthony-L" }, { "family_name": "Nagel", "given_name": "L. J.", "clpid": "Nagel-L-J" }, { "family_name": "Nicklow", "given_name": "R. M.", "clpid": "Nicklow-R-M" }, { "family_name": "Spooner", "given_name": "S.", "clpid": "Spooner-S" } ], "abstract": "We performed inelastic neutron-scattering measurements on powdered Ni3Al. The alloy was prepared in two states of chemical order: (1) with equilibrium L12 order, and (2) with disorder (the material was a fcc solid solution prepared by high-energy ball milling). Procedures to convert the energy loss spectra into approximate phonon density of states (DOS) curves for Ni3Al in the two states of chemical order were guided by Born\u2013von K\u00e1rm\u00e1n analyses with force constants obtained from previous single-crystal experiments on L12-ordered Ni3Al and fcc Ni metal. The main difference in the phonon DOS of the ordered and disordered alloys occurs near 39 meV, the energy of a peak arising from optical modes in the ordered alloy. These high-frequency optical modes involve primarily the vibrations of the aluminum-rich sublattice. The disordered alloy, which does not have such a sublattice, shows much less intensity at this energy. This difference in the phonon DOS around 39 meV is the main contributor to the difference in vibrational entropy of disordered and ordered Ni3Al, which we estimate to be Svibdis-Svibord=(+0.2\u00b10.1)kB/atom at high temperatures.", "doi": "10.1103/PhysRevB.52.3315", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1995-08-01", "series_number": "5", "volume": "52", "issue": "5", "pages": "3315-3321" }, { "id": "authors:8ffxm-cvw46", "collection": "authors", "collection_id": "8ffxm-cvw46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:OKAjap95", "type": "article", "title": "Short-range ordering in face-centered-cubic Ni3Al", "author": [ { "family_name": "Okamoto", "given_name": "J. K.", "clpid": "Okamoto-J-K" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Films of fcc Ni3Al with suppressed short-range order (SRO) were prepared by physical vapor deposition of Ni3Al onto room-temperature substrates. Extended electron energy-loss fine-structure spectra were obtained from both Al K and Ni L23 edges. After the samples were annealed for various times at 150 \u00b0C, a moderate growth of SRO was observed in the first-nearest-neighbor environments of both the Al and Ni atoms. As prepared, these fcc Ni3Al materials, and presumably others having similar heat evolutions as measured by differential scanning calorimetry, have a high degree of chemical disorder.", "doi": "10.1063/1.359463", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1995-05-01", "series_number": "9", "volume": "77", "issue": "9", "pages": "4380-4383" }, { "id": "authors:yvemm-0d687", "collection": "authors", "collection_id": "yvemm-0d687", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HONprb95a", "type": "article", "title": "Effects of ballistic atom movements on ordering transitions of binary alloys", "author": [ { "family_name": "Hong", "given_name": "L. B.", "clpid": "Hong-L-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We studied chemical order-disorder transitions in equiatomic alloys on a square lattice in the presence of both thermal and ballistic atom movements. Using Monte Carlo simulations with a vacancy mechanism, we determined the steady states of the alloys for various combinations of f (fraction of ballistic atom movements) and T (temperature), and located the order-disorder phase boundary on a diagram of T vs f. For symmetric interatomic potentials, the dynamical critical temperature decreased with f as (1-1.58f) when f\u22640.36, and decreased rapidly with f when 0.360.43. An Onsager-type kinetic rate equation was modified to include ballistic atom movements, and was used to identify two reasons why the ballistic atom movements suppress the dynamical critical temperature: (1) the ballistic atom movements dilute the enthalpy driving force for ordering, and (2) at low temperatures the ratio of thermal mobility coefficient to ballistic mobility coefficient becomes small.", "doi": "10.1103/PhysRevB.51.2687", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1995-02-01", "series_number": "5", "volume": "51", "issue": "5", "pages": "2687-2693" }, { "id": "authors:30cw6-dpw55", "collection": "authors", "collection_id": "30cw6-dpw55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANTprl94", "type": "article", "title": "Magnitude and Origin of the Difference in Vibrational Entropy between Ordered and Disordered Fe3Al", "author": [ { "family_name": "Anthony", "given_name": "L.", "clpid": "Anthony-L" }, { "family_name": "Nagel", "given_name": "L. J.", "clpid": "Nagel-L-J" }, { "family_name": "Okamoto", "given_name": "J. K.", "clpid": "Okamoto-J-K" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The difference in vibrational entropy between chemically disordered and DO3-ordered Fe3Al was measured by calorimetry to be (0.10 \u00b1 0.03) kB/atom at high temperatures, with the ordered alloy having the lower vibrational entropy. Analysis of the vibrational modes of the ordered and disordered alloys with a Born-von K\u00e1rm\u00e1n model showed that the lower vibrational entropy of the ordered alloy originates from high-frequency optical modes involving large-amplitude vibrations of the aluminum-rich sublattice.", "doi": "10.1103/PhysRevLett.73.3034", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1994-11-28", "series_number": "22", "volume": "73", "issue": "22", "pages": "3034-3038" }, { "id": "authors:0xsen-bjz88", "collection": "authors", "collection_id": "0xsen-bjz88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BANjap94", "type": "article", "title": "Phases and phase stabilities of Fe3X alloys (X=Al, As, Ge, In, Sb, Si, Sn, Zn) prepared by mechanical alloying", "author": [ { "family_name": "Bansal", "given_name": "C.", "clpid": "Bansal-C" }, { "family_name": "Gao", "given_name": "Z. Q.", "clpid": "Gao-Z-Q" }, { "family_name": "Hong", "given_name": "L. B.", "clpid": "Hong-L-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Mechanical alloying with a Spex 8000 mixer/mill was used to prepare several alloys of the Fe3X composition, where the solutes X were from groups IIB, IIIB, IVB, and VB of the periodic table. Using x-ray diffractometry and M\u00f6ssbauer spectrometry, we determined the steady-state phases after milling for long times. The tendencies of the alloys to form the bcc phase after milling are predicted well with the modified usage of a Darken\u2013Gurry plot of electronegativity versus metallic radius. Thermal stabilities of some of these phases were studied. In the cases of Fe3Ge and Fe3Sn, there was the formation of transient D03 and B2 order during annealing, although this ordered structure was replaced by equilibrium phases upon further annealing.", "doi": "10.1063/1.358375", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1994-11-15", "series_number": "10", "volume": "76", "issue": "10", "pages": "5961-5966" }, { "id": "authors:fsmdv-eja92", "collection": "authors", "collection_id": "fsmdv-eja92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PEAprb94", "type": "article", "title": "Measurements of 3d occupancy from Cu L2,3 electron-energy-loss spectra of rapidly quenched CuZr, CuTi, CuPd, CuPt, and CuAu", "author": [ { "family_name": "Pearson", "given_name": "D. H.", "clpid": "Pearson-D-H" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We used electron-energy-loss spectrometry to measure the intensities of the Cu white lines found at the onsets of the L2 and L3 absorption edges of rapidly quenched CuZr, CuTi, CuPd, CuPt, and CuAu. Enhancements of the white lines in the alloys as compared to elemental Cu were correlated with changes in the 3d occupancy of Cu atoms upon alloying. We found that the Cu atoms lost 0.2\u00b10.06 d electrons when alloyed with Ti or Zr, 0.0-0.0+0.06 d electrons when alloyed with Au or Pd, and 0.03-0.03+0.06d electrons when alloyed with Pt. We found no strong correlation between measured 3d-occupancy changes and heats of formation of the alloys, consistent with expectations that outer s electrons play an important role in the alloying of Cu with Pt, Pd, and Au.", "doi": "10.1103/PhysRevB.50.12969", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1994-11-01", "series_number": "17", "volume": "50", "issue": "17", "pages": "12969-12972" }, { "id": "authors:42pf3-f2d14", "collection": "authors", "collection_id": "42pf3-f2d14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb94", "type": "article", "title": "Local and nonlocal isomer shifts in bcc Fe-X alloys (X=Al,Si,Ga,Ge)", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Gao", "given_name": "Z-Q.", "clpid": "Gao-Z-Q" }, { "family_name": "Hamdeh", "given_name": "H. H.", "clpid": "Hamdeh-H-H" }, { "family_name": "Oliver", "given_name": "S. A.", "clpid": "Oliver-S-A" } ], "abstract": "We measured M\u00f6ssbauer spectra from bcc alloys of compositions near Fe3Al, Fe3Si, and Fe3Ge, and reanalyzed older data from Fe3Ga. All four alloys developed some D03 chemical order, and their M\u00f6ssbauer spectra were qualitatively similar. The local (first-nearest-neighbor) could be distinguished from the nonlocal (beyond the first-nearest-neighbor) contributions to the 57Fe isomer shifts from the solute atoms owing to differences in their hyperfine magnetic fields. The nonlocal isomer shift contributions correlated best to the valence of the solute atom, and not to the atomic volume. The local isomer shift contributions were best attributed to a loss of Fe 3d electrons at the solute sites.", "doi": "10.1103/PhysRevB.49.6312", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1994-03-01", "series_number": "9", "volume": "49", "issue": "9", "pages": "6312-6315" }, { "id": "authors:17fz6-6qe49", "collection": "authors", "collection_id": "17fz6-6qe49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LINjap94", "type": "article", "title": "Microstructural dependence of vacancy diffusion in ordered alloys", "author": [ { "family_name": "Lindsey", "given_name": "T. F.", "clpid": "Lindsey-T-F" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The dependence of the vacancy diffusional correlation factor on microstructure was investigated by Monte Carlo simulations (MCS). The MCS used activated state rate theory to model the vacancy diffusion. We varied the temperature, size of ordered domains, and the state of order within the domains. Correlations in the vacancy movement were found to vary widely, and numerical values are presented. Two different results were obtained, one for ordering in a homogeneous alloy and another for ordering in an alloy having domains. However, given the existence of domains, the vacancy correlation factor was observed to be independent of domain size. Oscillations in the correlation function were observed, and were attributed to pair trapping of the vacancy.", "doi": "10.1063/1.356381", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1994-02-01", "series_number": "3", "volume": "75", "issue": "3", "pages": "1467-1472" }, { "id": "authors:8h0gw-e4z68", "collection": "authors", "collection_id": "8h0gw-e4z68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HAMjap93", "type": "article", "title": "Structure and magnetic properties of sputtered thin films of Fe0.79Ge0.21", "author": [ { "family_name": "Hamdeh", "given_name": "H. H.", "clpid": "Hamdeh-H-H" }, { "family_name": "Oliver", "given_name": "S. A.", "clpid": "Oliver-S-A" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Gao", "given_name": "Z. Q.", "clpid": "Gao-Z-Q" } ], "abstract": "Films of Fe0.79Ge0.21 with thicknesses of 300 nm were synthesized by ion beam sputtering, and were annealed at temperatures from 200 to 550 \u00b0C. The materials were characterized by x-ray diffractometry, M\u00f6ssbauer spectrometry, vibrating sample magnetometry, ferromagnetic resonance spectrometry, and electrical resistivity measurements. The as-prepared materials comprised chemically disordered bcc crystallites of sizes less than 20 nm, and were found to have a distribution of internal strains. Upon annealing at temperatures of 250 \u00b0C and below, there occurred strain relaxation, some evolution of short range chemical order, and an improvement in soft magnetic properties. The coercive field was a minimum for the sample annealed at 250 \u00b0C. Crystallite growth occurred at higher annealing temperatures, accompanied by a transition in several measured parameters from those of ultrafine grained materials to those typical of polycrystalline materials. This trend can be explained with the random anisotropy model. M\u00f6ssbauer and magnetization measurements indicated that the Ge atoms behave as magnetic holes. The 57Fe hyperfine magnetic field distribution, and its change during chemical ordering, can be calculated approximately with a model of magnetic response. The large local isomer shifts at 57Fe atoms near Ge atoms suggest that a local depletion of 4s conduction electron density should be incorporated into the model.", "doi": "10.1063/1.354298", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1993-10-15", "series_number": "9", "volume": "74", "issue": "9", "pages": "5117-5213" }, { "id": "authors:csvd7-wtm60", "collection": "authors", "collection_id": "csvd7-wtm60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170816-153021431", "type": "article", "title": "A M\u00f6ssbauer spectrometry study of hyperfine magnetic fields and ordering in Fe_3Al", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Gao", "given_name": "Z. Q.", "clpid": "Gao-Z-Q" } ], "abstract": "Calculations of the ^(57)Fe hyperfine magnetic field distribution in Fe_3Al were performed with a model that assumed the exchange polarization mechanisms depend on the magnetic moments at atom sites. Calculations with parameters from dilute alloys were in semi-quantitative agreement with experiment, but the best agreement occurred when second and third-neighbor HMF perturbations were assumed to be small. The progress of the disorder \u2192 order transformation in Fe_3Al was measured by X-ray diffractometry and M\u00f6ssbauer spectrometry. Both techniques showed a transient appearance of B32-like order during the early stage of ordering at 300\u00b0C. The formation of transient B32 order is probably a kinetic phenomenon that cannot be predicted well by thermodynamics.", "doi": "10.1016/0168-583X(93)95153-V", "issn": "0168-583X", "publisher": "Elsevier", "publication": "Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms", "publication_date": "1993-04-04", "series_number": "1-4", "volume": "76", "issue": "1-4", "pages": "115-120" }, { "id": "authors:3xz52-ae580", "collection": "authors", "collection_id": "3xz52-ae580", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PEAprb93", "type": "article", "title": "White lines and d-electron occupancies for the 3d and 4d transition metals", "author": [ { "family_name": "Pearson", "given_name": "D. H.", "clpid": "Pearson-D-H" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We used electron-energy-loss spectrometry to measure the intensities of the white lines found at the onsets of the L2 and L3 absorption edges for most of the 3d and 4d transition metals. The intensities of the white lines, normalized to the trailing background, decreased nearly linearly with increasing atomic number, reflecting the filling of the d states. One-electron Hartree-Slater calculations of the white-line intensities were in good agreement with observed spectra. Empirical correlations between normalized white-line intensity and d-state occupancy provide a method for measuring changes in d-state occupancy due to alloying.", "doi": "10.1103/PhysRevB.47.8471", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1993-04-01", "series_number": "14", "volume": "47", "issue": "14", "pages": "8471-8478" }, { "id": "authors:b44zd-ek409", "collection": "authors", "collection_id": "b44zd-ek409", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANTprl93", "type": "article", "title": "Vibrational entropy of ordered and disordered Ni3Al", "author": [ { "family_name": "Anthony", "given_name": "L.", "clpid": "Anthony-L" }, { "family_name": "Okamoto", "given_name": "J. K.", "clpid": "Okamoto-J-K" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We have measured the difference in vibrational entropy of Ni3Al in two states of chemical order: as a disordered fcc solid solution, and as the equilibrium L12 ordered structure. Data were obtained from three independent methods: low-temperature calorimetry, temperature-dependent x-ray diffractometry, and temperature-dependent extended electron energy loss fine structure spectrometry. We estimate that at high temperatures, the vibrational entropy of chemically disordered Ni3Al is 0.3kB/atom greater than for ordered Ni3Al.", "doi": "10.1103/PhysRevLett.70.1128", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1993-02-22", "series_number": "8", "volume": "70", "issue": "8", "pages": "1128-1130" }, { "id": "authors:nnpqn-ahp29", "collection": "authors", "collection_id": "nnpqn-ahp29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180803-085352765", "type": "article", "title": "Effects of Thermal Cycling on the Physical Properties of VH_x", "author": [ { "family_name": "Bowman", "given_name": "R. C., Jr.", "orcid": "0000-0002-2114-1713", "clpid": "Bowman-R-C-Jr" }, { "family_name": "Lynch", "given_name": "F. E.", "clpid": "Lynch-F-E" }, { "family_name": "Marmaro", "given_name": "R. W.", "clpid": "Marmaro-R-W" }, { "family_name": "Luo", "given_name": "C. H.", "clpid": "Luo-C-H" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Cantrell", "given_name": "J. S.", "clpid": "Cantrell-J-S" }, { "family_name": "Chandra", "given_name": "D.", "clpid": "Chandra-D" } ], "abstract": "A thousand thermal cycles of vanadium hydride across the \u03b2-\u03b3 mixed phase region decreased the reversible hydrogen storage capacity and increased the absorption/desorption pressure hysteresis ratio. Thermal cycling also produced a large increase in hydride surface area. Nevertheless, X-ray diffraction and transmission electron microscopy showed the measured crystalline size to be larger after the 1000 cycles than for activated materials. These results were not anticipated from the behavior exhibited by other metal hydrides.", "doi": "10.1524/zpch.1993.181.Part_1_2.269", "issn": "0942-9352", "publisher": "De Gruyter", "publication": "Zeitschrift f\u00fcr Physikalische Chemie", "publication_date": "1993", "series_number": "1-2", "volume": "181", "issue": "1-2", "pages": "269-273" }, { "id": "authors:wjr2t-8g830", "collection": "authors", "collection_id": "wjr2t-8g830", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb91", "type": "article", "title": "Kinetics of short-range and long-range B2 ordering in FeCo", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "Short-range and long-range-order parameters were measured by M\u00f6ssbauer spectrometry and x-ray diffractometry during the disorder \u2192B2 order transformation in equiatomic FeCo. The change from a homogeneous mode of ordering at high temperatures to a heterogeneous mode of ordering at low temperatures was confirmed. By comparing parametric plots of the 57Fe hyperfine magnetic field versus long-range-order parameter for ordering in these two modes, an early independent relaxation of the short-range order was found in the kinetic path for homogeneous ordering. This relaxation was in reasonable agreement with estimates based on statistical kinetic theory.", "doi": "10.1103/PhysRevB.44.9805", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1991-11-01", "series_number": "18", "volume": "44", "issue": "18", "pages": "9805-9811" }, { "id": "authors:aws10-tgc55", "collection": "authors", "collection_id": "aws10-tgc55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150123-104047165", "type": "article", "title": "Shock wave consolidation of a Ni-Cr-Si-B metallic glass powder", "author": [ { "family_name": "Bach", "given_name": "J.", "clpid": "Bach-J" }, { "family_name": "Krueger", "given_name": "B.", "clpid": "Krueger-B" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "We studied parameters for the shock wave consolidation of a metallic glass powder, such as the effects of the shock wave energy and the shock wave duration. Microstructural characterizations of the compacts showed that some of them remained amorphous with porosity of about 1%, and that the shock wave propagated in a planar fashion causing large particle deformations. For our experimental parameters the energy range for a successful consolidation was between 140 and 200 J/g.", "doi": "10.1016/0167-577X(91)90139-W", "issn": "0167-577X", "publisher": "Elsevier", "publication": "Materials Letters", "publication_date": "1991-08", "series_number": "10-12", "volume": "11", "issue": "10-12", "pages": "383-388" }, { "id": "authors:4974s-x2t56", "collection": "authors", "collection_id": "4974s-x2t56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HAMprb90", "type": "article", "title": "Temperature dependence of hyperfine magnetic fields in Fe-Co alloys", "author": [ { "family_name": "Hamdeh", "given_name": "H. H.", "clpid": "Hamdeh-H-H" }, { "family_name": "Okamoto", "given_name": "J.", "clpid": "Okamoto-J-K" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "A M\u00f6ssbauer spectrometry study of bcc Fe-Co alloys was performed to measure the 57Fe hyperfine-field parameters from 77 to 900 K. The temperature dependence of the 57Fe hyperfine magnetic field in Fe-Co alloys was similar, although not identical, to that of 57Fe in pure Fe. These results are understood if the alignment of magnetic moments at Fe atoms is only slightly more temperature dependent than at Co atoms. This situation for Fe-Co is significantly different from that of Fe-Ni alloys, indicating that the interatomic exchange interactions in Fe-Co alloys are stronger than in Fe-Ni.", "doi": "10.1103/PhysRevB.42.6694", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1990-10-01", "series_number": "10", "volume": "42", "issue": "10", "pages": "6694-6696" }, { "id": "authors:13j2y-hpk95", "collection": "authors", "collection_id": "13j2y-hpk95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200812-151245571", "type": "article", "title": "Hyperfine magnetic fields in Fe\u2212Co alloys and their temperature dependences", "author": [ { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Hamdeh", "given_name": "Hussein", "clpid": "Hamdeh-Hussein" }, { "family_name": "Okamoto", "given_name": "James", "clpid": "Okamoto-James" } ], "abstract": "We obtained \u2075\u2077Fe hyperfine field parameters from Fe_(1\u2212x)-Co_ x alloys (0\u2264x\u22640.6) from 77 K to 900 K. We first discuss the origin of the low temperature hyperfine fields in terms of the 3d and 4s electrons at \u2075\u2077Fe atoms. The \u2075\u2077Fe hyperfine magnetic field (hmf) of Fe-Co alloys depends more weakly on temperature than the hmf of pure Fe. This temperature dependence occurs because the alignment of the magnetic moments at both the Fe atoms and at the Co atoms depend on temperature in the same way as the bulk magnetization of Fe-Co alloys.", "doi": "10.1007/bf02396131", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "1990-07", "series_number": "1-4", "volume": "54", "issue": "1-4", "pages": "799-803" }, { "id": "authors:g99nk-yxv84", "collection": "authors", "collection_id": "g99nk-yxv84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200812-135141888", "type": "article", "title": "Short range ordering in undercooled Fe\u2083Al", "author": [ { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Gao", "given_name": "Zheng-Qiang", "clpid": "Gao-Zheng-Qiang" }, { "family_name": "Hamdeh", "given_name": "Hussein", "clpid": "Hamdeh-Hussein" } ], "abstract": "Alloys of Fe-27 at.% Al were prepared far from thermodynamic equilibrium by ultra-rapid quenching from the melt. The hyperfine magnetic field (hmf) distribution revealed a wide variety of local Al environments around \u2075\u2077Fe atoms. Upon low temperature annealing, the probabilities of these different Al environments changed at different rates. The \"kinetic path\" of short range ordering in Fe\u2083Al is consistent with that found in a previous study of long range ordering, where B2 order grows more rapidly than D0\u2083 order at lower temperatures.", "doi": "10.1007/bf02396083", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "1990-07", "series_number": "1-4", "volume": "54", "issue": "1-4", "pages": "521-525" }, { "id": "authors:j3az1-dcq19", "collection": "authors", "collection_id": "j3az1-dcq19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200320-081243361", "type": "article", "title": "M\u00f6ssbauer study of mechanical alloying in Fe-V and Fe-C alloys", "author": [ { "family_name": "Le Ca\u00ebr", "given_name": "G.", "clpid": "Le-Ca\u00ebr-G" }, { "family_name": "Matteazzi", "given_name": "P.", "clpid": "Matteazzi-P" }, { "family_name": "Bauer-Grosse", "given_name": "E.", "clpid": "Bauer-Grosse-E" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Pianell", "given_name": "A.", "clpid": "Pianell-A" } ], "abstract": "M\u00f6ssbauer spectroscopy and X-ray diffraction have been used to characterize the microstructural changes which occur during ball milling of mixtures of iron and vanadium on the one hand and of iron and graphite on the other hand. The chemical compositions of the alloys are inhomogeneous during a large fraction of time of the synthesis. Almost all carbides and silicides may be synthetized by mechanical alloying.", "doi": "10.1051/jphyscol:1990417", "issn": "0449-1947", "publisher": "Les Ulis Cedex, France", "publication": "Journal de Physique Colloques", "publication_date": "1990-07", "series_number": "C4", "volume": "51", "issue": "C4", "pages": "151-155" }, { "id": "authors:gb0rz-kqh98", "collection": "authors", "collection_id": "gb0rz-kqh98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:OUYjap89", "type": "article", "title": "Percolation in alloys with thermally activated diffusion", "author": [ { "family_name": "Ouyang", "given_name": "H.", "clpid": "Ouyang-H" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "For diffusion in a real alloy, some concepts of formal percolation theory may need to be reconsidered because the \"immobile\" atoms are not truly immobile. Our Monte Carlo simulations of vacancy diffusion on bcc lattices show the existence of a relationship between the activation barrier heights for the vacancy-atom exchanges and the effective percolation threshold concentration. In the language of formal percolation theory, we have modeled this problem by varying the immobile species' barrier height from infinity to some finite value and calculating the resulting percolation threshold. When both species of atoms have a finite mobility, however, our results can be interpreted in terms of probabilities for vacancies to escape local clusters in a fixed amount of time. We find that the dynamical behavior undergoes a marked change above and below the formal percolation threshold, but the strength of the percolating cluster is much less important than in formal percolation theory.", "doi": "10.1063/1.343785", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1989-11-15", "series_number": "10", "volume": "66", "issue": "10", "pages": "4752-4755" }, { "id": "authors:qxz4c-33787", "collection": "authors", "collection_id": "qxz4c-33787", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:HAMprb89", "type": "article", "title": "M\u00f6ssbauer spectrometry study of the hyperfine fields and electronic structure of Fe-Co alloys", "author": [ { "family_name": "Hamdeh", "given_name": "H. H.", "clpid": "Hamdeh-H-H" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Pearson", "given_name": "D. H.", "clpid": "Pearson-D-H" } ], "abstract": "We obtained 57Fe hyperfine-field parameters from M\u00f6ssbauer spectra of Fe-Co alloys at 77 and 295 K. We also obtained the numbers of 3d electrons at Fe atoms by electron-energy-loss spectrometry (EELS). Together with bulk-magnetization data, we deduce how the occupancies of the 3d\u2191 and 3d\u2193 states at Fe atoms change with Co concentration. Changes in the total numbers of 3d electrons at Fe atoms were found to be small, with the M\u00f6ssbauer data indicating a maximum of about 0.2 electrons at 30 at. % Co, and the EELS data indicating a change of similar magnitude but of opposite sign. From both our isomer-shift and hyperfine-magnetic-field (HMF) data, we deduce a slight reduction in the occupancy of 4s states with Co concentration of dn4s/dc=-0.02 electrons, which is principally due to a loss of 4s\u2193 electrons. The model employed for the calculation of HMF distributions in terms of conduction- and core-electron polarizations worked well for disordered Fe-Co alloys, and was used to analyze the changes in HMF after the disorder\u2192order transformation. It showed that these HMF changes upon ordering are primarily due to changes in conduction-electron polarization.", "doi": "10.1103/PhysRevB.39.11233", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1989-06-01", "series_number": "16, pt", "volume": "39", "issue": "16, pt", "pages": "11233-11240" }, { "id": "authors:cp6cb-wwg91", "collection": "authors", "collection_id": "cp6cb-wwg91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201007-134245697", "type": "article", "title": "Kinetics of ordering in metallic alloys", "author": [ { "family_name": "Fultz", "given_name": "Brent", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Hamdeh", "given_name": "Hussein H.", "clpid": "Hamdeh-H-H" } ], "abstract": "Electrical, magnetic, and mechanical properties of metallic alloys depend on their state of chemical order. The systematic perturbations of \u2075\u2077Fe hyper-fine magnetic fields by solute atoms near \u2075\u2077Fe atoms can be used to measure the degree of order, provided that the systematics of these perturbations are properly understood. Although the equilibrium states of order in alloys are largely known, kinetic theories of the disorder \u2192 order transformation are still maturing, and M\u00f6ssbauer spectrometry can contribute to their development. Examples of how M\u00f6ssbauer spectrometry can be used to determine some novel features of ordering in ternary alloys are described.", "doi": "10.1007/bf02405872", "issn": "0304-3843", "publisher": "Springer", "publication": "Hyperfine Interactions", "publication_date": "1989-03", "series_number": "1-4", "volume": "45", "issue": "1-4", "pages": "55-72" }, { "id": "authors:jchph-dyz93", "collection": "authors", "collection_id": "jchph-dyz93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PEAapl88", "type": "article", "title": "Measurements of 3d state occupancy in transition metals using electron energy loss spectrometry", "author": [ { "family_name": "Pearson", "given_name": "D. H.", "clpid": "Pearson-D-H" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ahn", "given_name": "C. C.", "clpid": "Ahn-C-C" } ], "abstract": "We report a linear correlation between the total intensities of the L2,3 white lines in electron energy loss spectra and the number of unoccupied 3d states in 3d transition metals. We show that this correlation can be used to obtain quantitative information about electronic changes during alloying and during solid-state phase transformations.", "doi": "10.1063/1.100457", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "1988-10-10", "series_number": "15", "volume": "53", "issue": "15", "pages": "1405-1407" }, { "id": "authors:4m088-7tg98", "collection": "authors", "collection_id": "4m088-7tg98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120607-130518380", "type": "article", "title": "Intensities of backscatter M\u00f6ssbauer spectra", "author": [ { "family_name": "Mei", "given_name": "Z.", "clpid": "Mei-Z" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Morris", "given_name": "J. W., Jr.", "clpid": "Morris-J-W-Jr" } ], "abstract": "The intensities of \u03b3\u2010ray and x\u2010ray backscatter M\u00f6ssbauer spectra of ^(57)Fe nuclei in different matrix materials were studied theoretically and experimentally. A previous analysis by J. J. Bara [Phys. Status Solidi A 58, 349 (1980] showed that negative peak intensities occur in backscatter \u03b3\u2010ray spectra when the ^(57)Fe nuclei are in a matrix of light elements. We report a confirmation of this work and offer a simple explanation of the phenomenon. The present paper extends Bara's analysis to the case of conversion x\u2010ray spectra; expressions for the intensity of conversion x\u2010ray spectra as a function of absorber thickness and absorber material parameters are presented. We show that negative peak intensities are expected in conversion x\u2010ray spectra when the ^(57)Fe nuclei are in a matrix of heavy elements.", "doi": "10.1063/1.341641", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1988-09-01", "series_number": "5", "volume": "64", "issue": "5", "pages": "2550-2555" }, { "id": "authors:pvffb-wef12", "collection": "authors", "collection_id": "pvffb-wef12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULjcp88", "type": "article", "title": "An effect of antiphase boundaries on the kinetics of short-range ordering by a vacancy mechanism", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "In Monte Carlo simulations of chemical short-range ordering on a square lattice, the number of single-atom domains was found to depend on the presence of antiphase boundaries and on the mechanism by which ordering occurred. When antiphase boundaries were present and the ordering occurred by a vacancy mechanism, the number of single-atom domains was found to increase with decreasing temperature, in contrast to thermodynamic predictions. This is understood as a consequence of highly correlated vacancy motions in those regions of the lattice away from antiphase boundaries.", "doi": "10.1063/1.453917", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1988-03-01", "series_number": "5", "volume": "88", "issue": "5", "pages": "3227-3229" }, { "id": "authors:h1s0h-dg896", "collection": "authors", "collection_id": "h1s0h-dg896", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MENapl87a", "type": "article", "title": "Solid-state interdiffusion reactions in Ni/Ti and Ni/Zr multilayered thin films", "author": [ { "family_name": "Meng", "given_name": "W. J.", "clpid": "Meng-W-J" }, { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Ma", "given_name": "E.", "clpid": "Ma-E" }, { "family_name": "Johnson", "given_name": "W. L.", "clpid": "Johnson-W-L" } ], "abstract": "We have performed a comparative transmission electron microscopy study of solid-state interdiffusion reactions in multilayered Ni/Zr and Ni/Ti thin films. The Ni-Zr reaction product was amorphous while the Ni-Ti reaction product was a simple intermetallic compound. Because thermodynamic and chemical properties of these two alloy systems are similar, we suggest kinetic origins for this difference in reaction product.", "doi": "10.1063/1.98326", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "1987-08-31", "series_number": "9", "volume": "51", "issue": "9", "pages": "661-663" }, { "id": "authors:yeb2j-ztk16", "collection": "authors", "collection_id": "yeb2j-ztk16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULjcp87", "type": "article", "title": "Suppressed kinetics of short range ordering at low temperatures", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" } ], "abstract": "The kinetics of short range ordering in a binary alloy were studied by Monte Carlo simulation. Unlike the kinetics of ordering by the direct interchange of atoms, at low temperatures there is a marked suppression of the kinetics of ordering when ordering occurs by the vacancy mechanism. Large activation energies are associated with this suppression of kinetics. These activation energies suggest that certain heterogeneities in the atomic arrangements on the lattice behave as traps which the vacancy cannot easily escape at low temperatures. Such traps were observed during simulations of the ordering process.", "doi": "10.1063/1.453220", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1987-08-01", "series_number": "3", "volume": "87", "issue": "3", "pages": "1604-1609" }, { "id": "authors:py2ew-rtq45", "collection": "authors", "collection_id": "py2ew-rtq45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULprb86", "type": "article", "title": "Temperature dependence of hyperfine magnetic fields in Fe-Ni", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Morris", "given_name": "J. W., Jr.", "clpid": "Morris-J-W-Jr" } ], "abstract": "The 57Fe hyperfine magnetic field (HMF) distribution in bcc Fe-Ni alloys was calculated with a model of linear response of the 57Fe HMF to magnetic moments in the alloy. With the use of empirical parameters, the model largely accounts for the 57Fe HMF distribution at low temperatures. As shown by experiments with Si solutes in Fe-Ni, the anomalously strong temperature dependence of the 57Fe HMF in Fe-Ni is not due to the temperature dependence of the HMF response parameters. By analyzing the shape of the 57Fe HMF distribution, we find that this anomalous temperature dependence results from a large thermal sensitivity of the magnetic moments at those Fe atoms with more Ni atoms as nearest neighbors. This correlated with a strong temperature dependence of the recoil-free fraction and the second-order Doppler shift in Fe-Ni. We suggest that the large mean-square thermal displacement of Fe atoms in Fe-Ni is the cause of the anomalously strong temperature dependence, and we offer two explanations for this effect. Additionally, we have found evidence for a pseudodipolar interaction in Fe-Ni, and we also discuss the problems of parametrizing the 57Fe HMF solely in terms of the number of nearest neighbors of the 57Fe atom.", "doi": "10.1103/PhysRevB.34.4480", "issn": "0163-1829", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1986-10-01", "series_number": "7", "volume": "34", "issue": "7", "pages": "4480-4489" }, { "id": "authors:ef666-d8z46", "collection": "authors", "collection_id": "ef666-d8z46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:FULrsi78", "type": "article", "title": "Multichannel scaling with an eight bit microcomputer", "author": [ { "family_name": "Fultz", "given_name": "B.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B" }, { "family_name": "Morris", "given_name": "J. W., Jr.", "clpid": "Morris-J-W-Jr" } ], "abstract": "In this note a microcomputer-based system for multichannel scaling is described. This system relies on a combination of simple hardware with software support to achieve maximum cost effectiveness.", "doi": "10.1063/1.1135554", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1978-08", "series_number": "8", "volume": "49", "issue": "8", "pages": "1216" } ]