Impact of domains on the orthorhombic-tetragonal transition of BaTiO$_3$: an ab initio study

TL;DR

This study uses ab initio molecular dynamics to explore how domain walls affect phase transition temperatures and hysteresis in BaTiO$_3$, revealing that domain wall types and external fields can significantly modify material behavior.

Contribution

It demonstrates the impact of different domain walls on transition temperatures and hysteresis in BaTiO$_3$ using ab initio simulations, highlighting the role of elastic walls and external electric fields.

Findings

Domain walls significantly alter phase transition temperatures.

Elastic 90° domain walls reduce thermal hysteresis.

External electric fields further decrease hysteresis in certain domain configurations.

Abstract

We investigate the multi-domain structures in the tetragonal and orthorhombic phases of BaTiO$_3$ and the impact of the presence of domain walls on the intermediary phase transition. We focus on the change in the transition temperatures resulting from various types of domain walls and their coupling with an external electric field. We employ molecular dynamics simulations of an ab initio effective Hamiltonian in this study. After confirming that this model is applicable to multi-domain configurations, we show that the phase transition temperatures strongly depend on the presence of domains walls. Notably we show that elastic 90$^{\circ}$ walls can strongly reduce thermal hysteresis. Further analysis shows that the change in transition temperatures can be attributed to two main factors - long-range monoclinic distortions induced by walls within domains and domain wall widths. We also show that the coupling with the field further facilitates the reduction of thermal hysteresis for orthorhombic 90$^{\circ}$ walls making this configuration attractive for future applications.