Dissertations, Theses, and Capstone Projects

Date of Degree

1984

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Louis J. Massa

Committee Members

Angelo Santoro

John Lombardi

Subject Categories

Chemistry

Abstract

The interpretation of coherent x-ray diffraction experiments by a quantum model is described. Adjusting the coefficients of an LCAO expansion to best fit measured Bragg intensities results in a totally empirical quantum wavefunction. The quantum model is compared to a multipole expansion. The constraints imposed by quantum mechanics are examined, and several methods of satisfying these constraints while best fitting a wavefunction to measured Bragg intensities are detailed. Application is made to beryllium metal, with a resultant fit R(,1) = .00249. Similar applications to graphite and diamond are outlined. The formalism is extended to explicitly include solid-state effects, and this extension is applied to a model problem of an infinite line of hydrogen atoms. Neglect of solid-state effects can lead to errors of as much as 1% per electron. A more realistic treatment of crystal vibrations using a TLS model for external motions and 3N-6 spectroscopic-like local modes for internal motions is suggested. Related numerical algorithms are displayed. Directions for future work are suggested.

Comments

Digital reproduction from the UMI microform.

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