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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenSat, 13 Apr 2024 02:01:46 +0000I. The Investigation of the Alloy System Lead-Thallium. II. The Investigation of the Crystal Structure of the Complex of Hexamethylenetetramine with Manganous Chloride
https://resolver.caltech.edu/CaltechTHESIS:06082010-110159875
Authors: {'items': [{'id': 'Tang-You-Chi', 'name': {'family': 'Tang', 'given': 'You-Chi'}, 'show_email': 'NO'}]}
Year: 1950
DOI: 10.7907/NVF2-SD16
Part I: The Investigation of the Alloy System Lead-Thallium.
The lattice spacings for alloys in the lead phase of the
system lead-thallium were accurately determined. The
lattice-spacing-composition curve disagrees with that previously constructed
by Olander on the basis of his fewer determinations.
The new curve indicated that ordered phases PbTl_3 and PbTlTl_6
probably occur.
Part II: The Investigation of the Crystal Structure of the Complex
of Hexamethylenetetramine with Manganous Chloride.
Suitable crystals of the complex of hexamethylenetetramine
with manganous chloride were grown in a 1:1 mixture of alcohol
and acetone. By chemical analysis the composition was shown
to correspond to the formula, 2(CH_2)6N_4•MnCl_2•2H_20. The crystal
has a pseudo unit cell with a_1 = 11.80 Å., a_2 = 22.00 Å., a_3 =
7.21 Å., and Z = 4. The pseudo space group is C^9_(2v)-P2_1nb. A
few weak reflections indicate that the a_1 axis should be doubled,
but no account was taken of this in the present determination.
A trial structure derived from steric considerations and the
intensities of reflections h00 led to a satisfactory interpretation
of the Patterson distribution function. The approximate structure based
on the Patterson syntheses was confirmed by the Fourier projections
ρ(x) and ρ(y,x), and by calculation of structure factors for reflections
h00 and Okℓ.
The structure has the following important features. A manganese
atom lies on the common three-fold axis of two hexamethylenetetramine
molecules at the center of symmetry of a complex molecule, and the Mn-Cl
bonds are approximately perpendicular to the Mn-N bonds. Both the Patterson
syntheses andthe Fourier projections indicate that two molecules of
water are present in each complex molecule, and the Mn-O bonds are
approximately normal to the plane of the Mn-Cl and Mn-N bonds.
https://thesis.library.caltech.edu/id/eprint/5940Studies in Electron and X-Ray Diffraction : I. The Structure of Oxygen Fluoride. II. The Failure of the Born Approximation -- the Calculation of Complex Atomic Scattering Amplitudes for Electron Diffraction. III. Some Calculations of Atomic Form Factors. IV. Structural Studies by X-Ray Diffraction
https://resolver.caltech.edu/CaltechETD:etd-12032003-104507
Authors: {'items': [{'id': 'Ibers-James-Arthur', 'name': {'family': 'Ibers', 'given': 'James Arthur'}, 'orcid': '0000-0002-5418-3645', 'show_email': 'NO'}]}
Year: 1954
DOI: 10.7907/6K8R-3A92
In Part I the determination of the structure of oxygen fluoride by the method of electron diffraction is described.
In Part II the calculation of complex atomic scattering amplitudes and their ease in electron diffraction is discussed. Section A provides an outline of the theory and a summary of the calculations which have been made. In Section B some experimental work, the failure of the Born approximation, and the early calculations are described. In Section C the calculation of complex atomic scattering amplitudes from the partial waves scattering theory and the WKB method is described in detail.
In Part III the calculations of atomic form factors for a few selected atoms from Hartree-Fock anal Hartree radial wave functions are described.
In Part IV some structural studies by x-ray diffraction are described. In particular, a determination of the unit cell and space group of tetrapyridinecopper (II) fluoborate is described. A determination of the structure of potassium fluotitanate is presented. Finally, the work to date on the structure of monoclinic ceric iodate is presented. Included in this presentation is a detailed discussion of the various I. B. M. procedures used in the reduction of the large number of intensity data.https://thesis.library.caltech.edu/id/eprint/4735I. The Crystal Structure of Oxamide. ll. The Crystal Structure of 15,15'-Dehydro-β-Carotene
https://resolver.caltech.edu/CaltechETD:etd-01262004-143104
Authors: {'items': [{'id': 'Sly-William-Glenn', 'name': {'family': 'Sly', 'given': 'William Glenn'}, 'show_email': 'NO'}]}
Year: 1955
DOI: 10.7907/8GNV-3M53
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
I
A two-dimensional trial structure has been determined for oxamide by means of a Patterson projection. The analysis, which was the reinvestigation of a previous preliminary survey that had reported a slightly wavy planar structure with a 1.65 [Angstrom] C-C bond, was interrupted by the publication of an apparently satisfactory structure by Romers. The present study and two recent publications are in agreement both as to the parameters and space group of the triclinic unit cell, and the configuration of the molecule. The oxamide molecules are centered and they are hydrogen bonded into an essentially planar sheet which is parallel to the almost perfect cleavage plane exhibited by the crystals. The dimensions indicate that the C-C bond is a pure single bond and that the C-N bond has about 50% double-bond character as a result of resonance in the amide group. Oxamide, like oxalic acid and a few other related substances, is planar although the C-C bond apparently has no double-bond character.
II
The crystal structure of 15,15'-dehydrobetacarotene has been determined; this analysis represents the first conclusive study of any carotenoid. The analysis was accomplished through the use of a three-dimensional Patterson coupled with trial and error methods, and has been carried to a moderate state of refinement with Fourier projections, two-dimensional least squares, and a three-dimensional Fourier. The monoclinic unit cell has the parameters [...], [...], [...], and [...]; the space group is uniquely determined to be [...], which requires that the two molecules in the unit cell be centered. Except for the cyclohexene rings, the molecule is essentially plane with bond lengths and angles in general agreement with those predicted by theory and experiment. The chains are packed together almost unaffected by the cyclohexene rings. Each ring has the cis orientation about the single bond from ring to chain; the molecule is otherwise all trans. The molecules are efficiently packed, but the arrangement has resulted in a loss of resonance energy since the rings are not coplanar with the chain. The hypersymmetry of the molecules accounts for the deviation of the intensities from a normal statistical distribution.
A brief discussion of some of the IBM techniques used in the refinement of this structure has been included in the appendix.https://thesis.library.caltech.edu/id/eprint/353The Crystal Structure of Feist's Acid
https://resolver.caltech.edu/CaltechETD:etd-01202004-095607
Authors: {'items': [{'id': 'Petersen-Donald-Ralph', 'name': {'family': 'Petersen', 'given': 'Donald Ralph'}, 'show_email': 'NO'}]}
Year: 1955
DOI: 10.7907/SXC6-W012
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The crystal structure of Feist's acid, 1-methylenecyclopropane-trans-2,3-dicarboxylic acid, has been examined. The substance crystallizes in the triclinic system with space group [...]. Two enantiomorphous molecules of formula [...] are in the unit cell; the direct-cell constants are [...] and [...]. There is good cleavage at the face (010), and this is also the twinning plane.
The intensity data from equi-inclination Weissenberg photographs about each crystal axis were utilized in selecting and then refining a trial structure. Punched-card computing techniques were used to carry out least-squares refinements of atomic positions; two Fourier summations aided in final refinement. All refining work was based on full three-dimensional data.
Hydrogen bonds bind individual molecules into chains which extend in the [...] direction through the crystal. The methylene groups extended in the [...] direction form cogs on the chains, and two chains related by centers of symmetry are intermeshed closely.https://thesis.library.caltech.edu/id/eprint/246