Effects of ferroelectric polarization on surface phase diagram: an evolutionary algorithm study of the BaTiO$_{3}$(001) surface

TL;DR

This study uses an evolutionary algorithm to explore how ferroelectric polarization influences the surface phase diagram of BaTiO₃(001), revealing the potential to control surface stability via electric fields.

Contribution

It introduces a comprehensive surface structure prediction incorporating ferroelectric polarization, identifying stable reconstructions and their dependence on polarization.

Findings

Discovered a stable (2×1)-TiO surface reconstruction with experimental symmetry.

Found ferroelectric polarization can significantly alter surface free energy.

Demonstrated external electric fields can control surface stability.

Abstract

We have constructed the surface phase diagram of the BaTiO$_{3}$(001) surface by employing an evolutionary algorithm for surface structure prediction, where the ferroelectric polarization is included as a degree of freedom. Among over 1000 candidate structures explored, a surface reconstruction of (2$\times$1)-TiO is discovered to be thermodynamically stable and have the \emph{p2mm} plane group symmetry as observed experimentally. We find that the influence of ferroelectric polarization on the surface free energy can be either negligibly small or sizably large (over 1 eV per ($2 \times 1$) supercell), depending strongly on the surface structure and resulting in a significant distinction of surface phase diagram with varying ferroelectric polarization. It is therefore feasible to control the surface stability by applying an external electric field. Our results may have important implications in understanding the surface reconstruction of ferroelectric materials and tuning surface properties.