Regensburg 2016 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 23: Oxide Semiconductors I
HL 23.10: Vortrag
Dienstag, 8. März 2016, 12:15–12:30, H13
An ab initio study of defect complexes in Fe- and Gd-doped MgO co-doped with Li — •Sergey V. Levchenko, Sebastian Alarcon Villaseca, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, DE
Li/Fe- and Li/Gd-co-doped MgO have recently attracted attention due to their potential applications in catalysis and dosimetry [1,2]. In this work, we calculate formation energies of defect complexes in these materials using DFT with the hybrid PBE0 functional, and estimate their relative concentrations at realistic temperatures and oxygen pressures using the ab initio atomistic thermodynamics. We find that the FeMg-LiMg defect pairs are bound weaker than GdMg-LiMg pairs, and the dissociated FeMg-LiMg pairs are favored at elevated temperatures due to the increased configurational entropy. This explains why experimental EPR spectra of Gd3+ showed apparent changes upon Li-doping of Gd-MgO, while no changes have been detected in Li/Fe-MgO samples [3]. This qualitative result is found to be insensitive to the fraction of the exact exchange α in the hybrid functional for 0<α<0.5. – [1] U. Simon et al., Catal. Comm. 18, 132 (2012); [2] L.C. Oliveira, B.A. Doull, E.G. Yukihara, J. Luminescence 137, 282 (2013); [3] U. Simon, S. Arndt, T. Otremba, S. Alarcon Villaseca, S.V. Levchenko, M. Wollgarten, J.D. Epping, A. Kwasniewski, A. Berthold, F. Schmidt, O. Gorke, M. Scheffler, R. Schomacker, K.P. Dinse, in preparation.