Simulating Small Polarons from First Principles: The DFT supercell approach

Sebastian Kokott (FHI der MPG Berlin)

Dec 13. 2019, 11:00 — 11:40

Kohn-Sham density functional theory (DFT) can be used to simulate small polarons in the adiabatic, strong-coupling limit. Accordingly, it is understood as the ab initio successor of Pekar’s Polaron [1]. In this talk, we review two methods to predict small-polaron energies using the supercell approach. That is, 1) the conventional “charge in a supercell” approach and 2) the approach introduced by Sadigh et al. [2]. For each approach the calculated polaron properties are tested in two ways: Their dependence on the underlying exchange-correlation functional and convergence with the supercell size. As a result, we propose a correction for approach 2), which allows obtaining numerically converged results in moderately sized supercells using (computationally cheap) semi-local XC functionals [3]. Eventually, we present a systematic investigation of the polaron potential energy surface unfolding challenging issues for sampling methods like molecular dynamics.

[1] S.I. Pekar, Zh. Eksp. Teor. Fiz 16, 335 (1946)
[2] B. Sadigh et al., Phys. Rev. B 92, 075202 (2015)
[3] S. Kokott et al., New J. Phys. 20, 033023 (2018)

Further Information
ESI Boltzmann Lecture Hall
Associated Event:
Polarons in the 21st Century (Workshop)
Jozef Devreese (U Antwerpen)
Cesare Franchini (U of Vienna)
Georg Kresse (U of Vienna)
Jacques Tempere (U Antwerpen)