Accession Number : ADA321969

Title :   First Principles Theoretical Studies of Ferroelectric Lattice Instabilities.

Descriptive Note : Final rept. 1 Feb 91-31 Jan 97,

Corporate Author : NEBRASKA UNIV LINCOLN

Personal Author(s) : Hardy, John R.

PDF Url : ADA321969

Report Date : 01 FEB 1997

Pagination or Media Count : 10

Abstract : Work performed over the past six years is described. Studies have ranged over a variety of halide based materials (principally fluorides) in which the oxygen in oxide ferroelectrics is replaced by fluorine. For these systems, the use of free ion wavefunctions to calculate Gordon-Kim parameter-free modified electron gas potentials leads, overall, to good agreement with experiment and predicts the existence of ferroelectric phases for certain of these systems that have yet to be synthesized. We also have performed work on the oxide-based systems based on the potential-induced-breathing (PIB) model which permits spherical distortion of the 02- charge density. While this does not lead to ferroelectricity, it has a significant effect on the ferroelastic transitions associated with rotational instabilities of the oxygen octahedra. Finally, we have examined the effects of free surfaces on ferroelectric behavior and find them to be large.

Descriptors :   *PHASE TRANSFORMATIONS, *FERROELECTRIC MATERIALS, ELECTRON GAS, TRANSITION TEMPERATURE, CHARGE DENSITY, WAVE FUNCTIONS, FLUORIDES.

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE