Phase Transitions and Antiferroelectrivity in BiFeO3 from Atomic Level Simulations

TL;DR

This study uses atomistic simulations to explore phase transitions and antiferroelectric behavior in BiFeO3, revealing a direct transition between ferroelectric and orthorhombic phases and the microscopic mechanisms involved.

Contribution

It introduces a shell model fitted to first-principles calculations to simulate finite-temperature properties of BiFeO3, uncovering detailed phase transition pathways.

Findings

Direct transition from R3c to Pbnm phase without intermediate phases

Presence of two sublattices with opposite polarizations at high temperature

Double-hysteresis loop characteristic of antiferroelectric behavior

Abstract

The structural and polar properties of BiFeO3 at finite temperature are investigated using an atomistic shell model fitted to first-principles calculations. Molecular Dynamics simulations show a direct transition from the low-temperature R3c ferroelectric phase to the Pbnm orthorhombic phase without evidence of any intermediate bridging phase between them. The high-temperature phase is characterized by the presence of two sublattices with opposite polarizations, and it displays the characteristic double-hysteresis loop under the action of an external electric field. The microscopic analysis reveals that the change in the polar direction and the large lattice strains observed during the antiferroelectric-ferroelectric phase transition originate from the interplay between polarization, oxygen octahedron rotations and strain. As a result, the induced ferroelectric phase recovers the symmetry of the low temperature R3c phase.