Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

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

O 59.7: Vortrag

Mittwoch, 18. März 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).