Efficient local atomic cluster expansion for BaTiO$_3$ close to equilibrium

TL;DR

This paper develops efficient atomic cluster expansion models for BaTiO$_3$ that accurately reproduce phase transitions and defect properties, with or without explicit Coulomb interactions, enabling fast simulations of this ferroelectric material.

Contribution

The work introduces two ACE models for BaTiO$_3$ that effectively capture phase transitions and defect properties, comparing implicit and explicit Coulomb interaction treatments.

Findings

Both models accurately describe temperature-induced phase transitions.

Models effectively simulate properties of defects like vacancies and domain walls.

Explicit Coulomb treatment does not significantly improve accuracy.

Abstract

Barium titanate (BTO) is a representative perovskite oxide that undergoes three first-order ferroelectric phase transitions related to exceptional functional properties. In this work, we develop two atomic cluster expansion (ACE) models for BTO to reproduce fundamental properties of bulk as well as defective BTO phases. The two ACE models do not target full transferability but rather aim to examine the influence of implicit and explicit treatment of long-range Coulomb interactions. We demonstrate that both models describe equally well the temperature induced phase transitions as well as polarization switching due to applied electric field. Even though the parametrizations are based on a limited number of configurations that are mostly not far away from the equilibrium, the ACE models are able to capture also properties of important crystal defects, such as oxygen vacancies, stacking faults and domain walls. A systematic comparison shows that the phase transitions as well as the fundamental properties of the investigated defects can be described with similar accuracy with or without explicit treatment of charges and Coulomb interactions allowing for efficient short-range machine learning potentials.