Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 74: Focussed session: Theory and computation of electronic structure: new frontiers VI (jointly with HL, DS)

O 74.6: Vortrag

Donnerstag, 17. März 2011, 16:15–16:30, TRE Phy

Quasiparticle calculations of core levels — •Arno Schindlmayr and Dominik Biffart — Department Physik, Universität Paderborn, 33095 Paderborn, Germany

Electrons that occupy core orbitals are tightly bound to the atomic nucleus and do not participate in chemical bonding. Nevertheless, their binding energies are sensitive to the chemical environment, because the redistribution of the valence electrons due to bond formation strongly influences the interaction with the nucleus. For this reason, core-level spectroscopy is an important tool to clarify the atomic structure of materials, such as the geometry of surfaces, interfaces or defects, which can be used even when direct imaging techniques are not applicable. Theoretical calculations of core levels are typically based on density-functional theory. Although these often show the correct trends, they are plagued by the well known deficiencies of common exchange-correlation functionals as well as technical difficulties, especially in the prevalent pseudopotential approximation. As an alternative, we employ many-body perturbation theory, where the quasiparticle correction to the Kohn-Sham eigenvalues provides a formally exact description of dynamical screening around the core hole in the final state. Our implementation is based on the full-potential linearized augmented-plane-wave (FLAPW) method and employs the GW approximation for the electronic self-energy. The calculated core levels of selected systems, such as silicon in various crystalline materials with differing local environments, are in very good quantitative agreement with experimental data from X-ray photoemission measurements.