Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 83: Surface Chemistry and Growth
O 83.10: Talk
Thursday, March 19, 2015, 12:45–13:00, MA 144
Theoretical evidence for unexpected O-rich phases at corners of MgO surfaces — Saswata Bhattacharya1, Daniel Berger2, Karsten Reuter2, •Sergey V. Levchenko1, Luca M. Ghiringhelli1, and Matthias Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin, DE — 2Technische Universität München, Garching, DE
Introducing charge carriers into MgO via p doping greatly reduces formation energy of an O-vacancy in the bulk and at the (100) surface [1]. In this work, we use hybrid density functional theory to explore O-vacancy and O/O2-ad-species defects at corners of MgO surfaces. The defects are modelled using MgO clusters embedded into a field of norm-conserving pseudopotentials and point charges. The long-range response of the oxide to the charge carriers trapped at the defects is taken into account using a polarizable force field. The low-energy defect atomic structures are found using an ab initio genetic algorithm [2]. Concentrations of O-vacancies and O-ad-species at realistic temperatures and pressures are obtained with ab initio atomistic thermodynamics. Unexpectedly, we find that O-ad-species rather than O-vacancies are dominating defects at realistic conditions. The stability of the O-ad-species over O-vacancies and pristine corners is explained by an interplay between bond-breaking, bond-making, and charge-carrier trapping. − [1] N. Richter et al., Phys. Rev. Lett. 111, 045502 (2013); [2] S. Bhattacharya et al., New J. Phys., in press (2014).