Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 8: Surface State Spectroscopy I

O 8.6: Vortrag

Montag, 7. März 2016, 12:00–12:15, H4

Ab initio core-level spectroscopy for large systems: Comparison of ground-state density-functional based approximations — •Georg S. Michelitsch, Katharina Diller, Reinhard J. Maurer, and Karsten Reuter — Technische Universität München

Core-level spectroscopy experiments such as Near-Edge X-Ray Absorption Fine-Structure (NEXAFS) allow to sensitively probe the electronic states of gas-phase and surface-adsorbate systems. Particularly for surface-adsorbate systems the complexity of the experimental signatures requires independent first-principles calculations for a reliable analysis. For corresponding system sizes, numerically efficient core-level constraining approaches based on density-functional theory (DFT) are presently the method of choice. Different flavors of this approximate approach vary by different occupations of both the initial core level and the final virtual orbital participating in the electron excitation processes. We systematically benchmark these flavors against experimental K-edge data from a library of organic compounds representing building blocks of organic adsorbates like benzene or porphine. Assessing different DFT functionals, we generally find relative peak positions in the near-edge region to already be well reproduced at the semi-local level. With respect to the different flavors the transition potential approach [1] consistently yields most reliable transition energies and intensities.

[1] L. Triguero, L.G.M. Petterson, and H. Agren, Phys. Rev. B 58, 8097 (1998).