Regensburg 2016 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 38: Oxide Semiconductors II

HL 38.2: Vortrag

Dienstag, 8. März 2016, 15:00–15:15, H13

Hybrid density functional calculations of small polarons and bi-polarons in oxides — •Sebastian Kokott, Sergey V. Levchenko, and Matthias Scheffler — Fritz Haber Institute of the MPS, Berlin, Germany

Formation of polarons, i.e. phonon-“dressed” holes or electrons, plays an important role in optical spectra and electrical conductivity of materials. For the formation of small (localized) polarons microscopic properties of the systems are crucial, and the use of an ab initio theory is necessary for its description. For this reason we calculate small polarons in a supercell approach using density functional approximations (DFA).
We find that the results can be strongly affected by self-interaction and finite supercell size errors. However, using constraints from exact DFT, such as the IP-theorem[1], the binding energy of polarons can be reformulated in terms of energies obtained from the neutral system[2]. With this we show, that the dependence on the underlying XC functional of the reformulated polaron binding energy can be drastically reduced. The effect will be demonstrated for small polarons and bi-polarons in MgO for the entire range of the the exact-exchange fraction in the HSE hybrid functional. We also demonstrate the dependence of the results on the supercell size and give results on the binding energies of polarons in the extrapolated dilute limit.
[1] J. Perdew et al., Phys. Rev. Lett. 49, 1691 (1982) [2] B. Sadigh Phys. Rev. B 92, 075202 (2015)