Some Problems in the Theory of Perovskite Ferroelectrics

Abstract

A brief review is given on the studies of ferroelectricity in perovskites. Early phenomenological theories of displacement-type ferroelectrics are considered. Two markedly different approaches based on density-functional theory are described. In one approach, the electron density of crystal is determined as a sum of Bloch functions. In the other, it is constructed as a superposition of the electron densities of individual ions. The latter approach gives a microscopic justification for the old phenomenological theories. We show that some phenomena in perovskites, which seemingly are of the order–disorder origin, can be explained by quasi-one-dimensional peculiarities of lattice dynamics.

Keywords:

• Theory of ferroelectricity
• perovskites
• lattice dynamics
• phase transformations
• disorder

Acknowledgments

The authors are grateful to V. L. Ginzburg for permanent support of our efforts in studying ferroelectrics. This work was financially supported in part by the Leading Scientific Schools Program, Presidium and the Branch of Physical Sciences, Russian Academy of Sciences, and the RFBR grant No. 05-02-17359.