Date of Degree
Louis J. Massa
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.
Goldberg, Martin Jeffry, "Totally Empirical Wavefunctions from X-Ray Diffraction Data" (1984). CUNY Academic Works.