Ab initio investigation of competing instabilities in ferroelectric perovskite PbTiO3

TL;DR

This study uses first-principles models to analyze the complex interplay of structural instabilities in ferroelectric PbTiO3, revealing how competing modes significantly influence its phase transition temperature.

Contribution

The paper introduces a novel first-principles modeling approach to investigate the lattice instabilities and their interactions in ferroelectric perovskite PbTiO3.

Findings

Competing ferroelectric and antiferrodistortive modes drastically affect PbTiO3 properties.

Interaction between soft modes shifts the Curie temperature by hundreds of degrees.

Theoretical insights explain the dynamical nature of these instabilities.

Abstract

We have developed first-principles models, based on a general parametrization of the full potential-energy surface, to investigate the lattice-dynamical properties of perovskite oxides. We discuss the application of our method to prototypic ferroelectric PbTiO3, showing that its properties are drastically affected by a competition between structural instabilities. Indeed, we confirm previous indications that the destructive interaction between the ferroelectric and antiferrodistortive (involving rotations of the O6 octahedra) soft modes shifts PbTiO3's Curie temperature by hundreds of degrees. Our theory provides unique insight into this gigantic effect and its dynamical character.