First-principles Landau-like potential for BiFeO$_3$ and related materials

TL;DR

This paper develops a simple Landau-like potential model for BiFeO$_3$ and related materials, derived from first-principles calculations, to understand phase stability and interactions.

Contribution

It introduces an analytical method to compute Landau-like model parameters directly from density functional theory for BiFeO$_3$ and doped variants.

Findings

Accurately captures first-principles results

Identifies key interactions controlling phase stability

Provides a predictive model for material behavior

Abstract

In this work we introduce the simplest, lowest-order Landau-like potential for BiFeO$_3$ and La-doped BiFeO$_3$ as an expansion around the paraelectric cubic phase in powers of polarization, FeO$_6$ octahedral rotations and strains. We present an analytical approach for computing the model parameters from density functional theory. We illustrate our approach by computing the potentials for BiFeO$_3$ and La$_{0.25}$Bi$_{0.75}$FeO$_3$ and show that, overall, we are able to capture the first-principles results accurately. The computed models allow us to identify and explain the main interactions controlling the relative stability of the competing low-energy phases of these compounds.