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Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Oxide and Insulator Surfaces: Structure, Epitaxy and Growth

O 59.7: Talk

Wednesday, March 18, 2015, 16:30–16:45, MA 042

First-Principles Embedded Cluster Calculations of Surface Defects at TiO2(110) — •Daniel Berger, Harald Oberhofer, and Karsten Reuter — Technische Universität München

Bulk and surface defects critically determine many of the properties and functions that make TiO2 such an interesting and widely studied material. Given this importance, it is both surprising and discomforting to see how little is actually known especially about the surface defects of TiO2. For surface oxygen vacancies not even their thermodynamically favored charge state is unambiguously clear. We contribute to this context with first-principles embedded cluster calculations [1] of the rutile TiO2(110) surface. Our approach allows for a numerically particularly efficient application of hybrid density-functional theory inside the quantum mechanic (QM) cluster region. In the extended molecular mechanic (MM) embedding region specifically optimized interatomic potentials provide a quantitative account of the strong TiO2 polarization response. We discuss the advantages of this QM/MM approach against more common periodic supercell calculations especially for charged O vacancies. Over a wide range of electrochemical potentials and oxygen partial pressures our calculations show the +2 state to be thermodynamically favored, which can be rationalized by the huge dielectric constant of TiO2.

[1] D. Berger et al., J. Chem. Phys. 141, 024105 (2014).

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