Full potential LMTO calculations for perovskites

Abstract

First principles “frozen phonon” calculations based on the Density-Functional-Theory and a new Linear-Muffin-Tin-Orbital method were performed for BaTiO₃ and SrTiO₃. The ferroelectric lattice instability of BaTiO₃ was reproduced by the calculation without any adjustable parameter. Investigations of the relationship between electronic structure and crystal structure showed that the nonbonding Op states in the upper part of the cubic valence band become bonding in the tetragonal phase. They thus lower the energy of the low symmetry structure.