Microscopic Theory of Phonon Spectra in Normal Solids.
Abstract
A theory of lattice dynamics is developed for a normal solid considered as a manybody system of interacting nuclei and electrons. The nuclei are taken to move about some equilibrium positions with small amplitudes (harmonic approximation), while the electrons are unrestricted, i.e., the adiabatic, or BornOppenheimer, approximation is not made. Within the harmonic approximation the response function obeys a closed equation, in which the full influence of the electrons is rigorously described by their dielectric function, (or susceptibility, or conductivity). This result, which is not restricted by the adiabatic approximation, is valid for all normal solids, insulators, metals, semiconductors, or semimetals. The twoband model of such a general solid demonstrates that acoustic phonons for small wave vectors can always exist beyond the adiabatic approximation.
 Publication:

Ph.D. Thesis
 Pub Date:
 July 1976
 Bibcode:
 1976PhDT........45P
 Keywords:

 Physics: Condensed Matter;
 Approximation;
 Band Structure Of Solids;
 Crystal Lattices;
 Phonons;
 Dielectrics;
 Dynamic Response;
 Harmonic Motion;
 Lattice Vibrations;
 Neutron Scattering;
 Nonadiabatic Theory;
 SolidState Physics