Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 50: Oxide and Insulator Surfaces I

O 50.10: Talk

Wednesday, April 2, 2014, 12:45–13:00, WIL A317

Ab-initio study of the wurtzite terminated rocksalt CoO(111) polar surface: Facing a DFT bulk dilemma — Florian Mittendorfer and •Josef Redinger — Inst. f. Applied Physics, Vienna University of Technology, Vienna, Austria

Evidenced by LEED, the polar (111) surface of CoO is terminated by a wurtzite like top Co-O bilayer, which from experimental and theoretical evidence is believed to become metallic to compensate polarity [1]. An ab-initio DFT investigation of such a mechanism is not only complicated by the polarity of the surface, but also by the correlated nature of the Co 3d electrons, which have to be treated by PBE+U type approaches or by employing hybrid functionals like HSE06. Using the VASP code slabs of various thickness have been treated and the preference for a wurtzite like termination could be established. However, this outcome should be taken with caution, since already for the CoO bulk system PBE+U and HSE06 find a preference for the wurtzite (or zincblende) structure over the experimental slightly distorted rocksalt structure, similar to the case of MnO [2]. We present an analysis of our HSE06 and PBE+U results also for different double counting corrections and conclude that only for unreasonably high values of U the correct bulk phase order can be established.
K Heinz and L Hammer, J. Phys.: Condens. Matter 25, 173001 (2013 Review)
A. Schrön, C. Rödl, and F. Bechstedt, Phys. Rev. B 82, 165109 (2010)