First-principles study of lattice instabilities in Ba_xSr_(1-x)TiO_3

摘要

Using first-principles calculations based on a variational density functionalperturbation theory, we investigate the lattice dynamics of solid solutions ofbarium and strontium titanates. Averaging the information available for therelated pure compounds yields results equivalent to those obtained within thevirtual crystal approximation, providing frequencies which are a goodapproximation to those computed for a (111) ordered supercell. Using the sameaveraging technique we report the evolution of the ferroelectric andantiferrodistortive instabilities with composition.