Accession Number : AD0664942

Title :   EXPERIMENTAL AND THEORETICAL STUDY OF LATTICE DYNAMICS.

Descriptive Note : Final rept. 19 Sep 66-18 Sep 67,

Corporate Author : GULF GENERAL ATOMIC INC SAN DIEGO CALIF

Personal Author(s) : Borgonovi,G. M.

Report Date : SEP 1967

Pagination or Media Count : 104

Abstract : The possibility of making studies of lattice dynamics using a linear electron accelerator as a neutron source has been investigated. The methods of filter analyzer and crystal analyzer have been studied both experimentally and theoretically. The single differential angular cross sections were measured and results were compared to a calculation made on the basis of a lattice dynamical model. Experiments on aluminum show that this method is inherently sensitive enough to allow the check of a lattice dynamical model. Sharp peaks arise in the angular cross section whenever the velocity of the scattered neutron is equal to the phase velocity of the phonon responsible for the scattering process. A lattice dynamical model has been produced for the system MgO. The calculation is based on the formalism of the shell model with noncentral interactions extended to second neighbors. The parameters are derived from the known elastic and dielectric constants. The full dispersion relations for symmetry directions, the frequency spectrum, and the specific heat of MgO have been calculated.

Descriptors :   (*CRYSTAL LATTICES, *NEUTRON SCATTERING), INFRARED RADIATION, INELASTIC SCATTERING, LINEAR ACCELERATORS, SINGLE CRYSTALS, DIFFERENTIAL CROSS SECTIONS, NUCLEAR MODELS, SYMMETRY(CRYSTALLOGRAPHY), SPECIFIC HEAT, BRILLOUIN ZONES, MAGNESIUM OXIDES, ALUMINUM, PHONONS, INTERACTIONS, ELASTIC PROPERTIES, DIELECTRIC PROPERTIES

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE