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 (el-ph) 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 el-ph coupling. Using our correction approach, we present accurate all-electron full-potential DFT results for small polarons in rocksalt MgO and rutile TiO2.
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Kokott, S., Levchenko, S. V., Rinke, P., & Scheffler, M. (2018). First-principles supercell calculations of small polarons with proper account for long-range polarization effects. New Journal of Physics, 20(3). https://doi.org/10.1088/1367-2630/aaaf44