Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 28: Electronic Structure Theory: General I

O 28.3: Vortrag

Dienstag, 13. März 2018, 11:00–11:15, MA 141

A new design principle for embedded cluster models? Embedded-cluster calculations of surface oxygen vacancies at TiO₂. — •Matthias Kick, Karsten Reuter, and Harald Oberhofer — Technische Universität München

Surface oxygen vacancies, in particular their nature as charge trapping centers, play an important role for many oxide materials properties. However, addressing them with first-principles density-functional theory (DFT) computations remains a challenge. At least Hubbard corrected DFT+U is required to achieve an appropriate electron localization. At the same time, the large dielectric constant of polarizable oxides like TiO₂ leads to a strong polarization response. As a result supercells of increasing size are necessary in order to avoid spurious interactions between periodic images in case of charged defects, rendering the conventional periodic boundary condition supercell approach impractical. We combine the solid state (QM/MM) embedding functionality in FHI-aims with DFT+U, yielding a numerically most efficient approach to treat the aperiodic aspects at oxide surface. Systematic calculations of neutral and charged states of the surface oxygen vacancy at rutile TiO₂ (110) show that the shapes of the embedded cluster models are crucial for a proper description of surface phenomena. We assess this problem by proposing a new design principle for embedded clusters.