Dynamic microscopic structures and dielectric response in the cubic-to-tetragonal phase transition for BaTiO3 studied by first-principles molecular dynamics simulation

TL;DR

This study uses first-principles molecular dynamics to investigate the dynamic structures and dielectric response of BaTiO3 during the cubic-to-tetragonal phase transition, revealing the transition mechanism and dielectric behavior.

Contribution

It provides a detailed first-principles analysis of phase transition dynamics and dielectric properties in BaTiO3, clarifying the nature of the soft mode and dielectric response above Tp.

Findings

Phase transition driven by condensation of transverse correlations

Soft mode frequency saturates near 60 cm-1 near Tp

Dielectric function exhibits two-mode feature above Tp

Abstract

The dynamic structures of the cubic and tetragonal phase in BaTiO3 and its dielectric response above the cubic-to-tetragonal phase transition temperature (Tp) are studied by first-principles molecular dynamics (MD) simulation. It's shown that the phase transition is due to the condensation of one of the transverse correlations. Calculation of the phonon properties for both the cubic and tetragonal phase shows a saturation of the soft mode frequency near 60 cm-1 near Tp and advocates its order-disorder nature. Our first-principles calculation leads directly to a two modes feature of the dielectric function above Tp [Phys. Rev. B 28, 6097 (1983)], which well explains the long time controversies between experiments and theories.