First-Principles Supercell Calculations of Small Polarons with Proper Account for Long-Range Polarization Effects

TL;DR

This paper introduces a supercell DFT method that accurately models small polarons by accounting for long-range polarization effects, reducing supercell size dependence and improving result reliability.

Contribution

The authors develop a correction scheme for DFT polaron calculations that minimizes supercell size and functional dependence, enhancing accuracy in modeling small polarons.

Findings

Effective correction scheme reduces supercell size dependence.

Accurate DFT results for polarons in MgO and TiO2.

Long-range electrostatic and electron-phonon effects are key factors.

Abstract

We present a density functional theory (DFT) based supercell approach for modeling small polarons with proper account for the long-range elastic response of the material. Our analysis of the supercell dependence of the polaron properties (e.g., atomic structure, binding energy, and the polaron level) reveals long-range electrostatic effects and the electron-phonon interaction as the two main contributors. We develop a correction scheme for DFT polaron calculations that significantly reduces the dependence of polaron properties on the DFT exchange-correlation functional and the size of the supercell in the limit of strong electron-phonon coupling. Using our correction approach, we present accurate all-electron full-potential DFT results for small polarons in rocksalt MgO and rutile TiO$_2$.