Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 97: Heterogeneous catalysis II

O 97.3: Talk

Friday, March 18, 2011, 11:45–12:00, PHY C213

Oxygen vacancies in different charge states at the MgO(100) surface — •Norina A. Richter, Sergey V. Levchenko, and Matthias Scheffler — Fritz-Haber-Institut, Berlin (Germany)

Point defects can dramatically change the chemical properties of oxide surfaces. However, the concentration of the defects at realistic conditions is difficult to determine experimentally. In this work, we calculate electronic structure and formation energies of neutral and charged oxygen vacancies in the bulk and at the MgO(100) surface [1], and estimate their concentration and distribution at realistic temperatures and pressures using the ab initio atomistic thermodynamics approach [2]. We determine the stability of different charge states of the oxygen vacancy as a function of the Fermi level position within the band gap (simulating the global effect of doping). We also analyze how the proximity of a dopant providing localized acceptor states changes the vacancy formation energies (local effect of doping). We use the Li substitutional defect as a prototype of such a dopant. The effects of electron exchange and correlation on our results, in particular the self-interaction error and the band-gap problem, are discussed, based on comparison of LDA with the HSE06 functional with different values of the exchange screening parameter.