Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 41: Ab-initio approaches to excitations in condensed matter I

O 41.3: Vortrag

Mittwoch, 25. März 2009, 15:30–15:45, SCH 251

Static Correlation in the Description of the Oxygen-Metal Interaction — •Christian Carbogno and Axel Groß — Institut für Theoretische Chemie, Universität Ulm,

The correct treatment of static correlation, i.e. the necessity to include multiple determinants to describe a wave function of a certain symmetry, is critical for the correct simulation of molecules, particularly if excited open-shell singlet states are addressed. Whereas these effects can be tackled unambiguously with CI, only an approximative description in terms of fractional occupation numbers is possible when solving the Kohn-Sham equations. For extended systems, where DFT methods are widely applied due to their numerical efficiency, such effects are typically negligible, especially if the interaction of a molecule with a metal surface is addressed. The thereby occurring adiabatic charge transfer, as described within the Born-Oppenheimer approximation, generally breaks the symmetry of the molecule: Thus one basic requirement for the manifestation of static correlation gets lost. For the oxygen chemistry on metal substrates, however, the Born-Oppenheimer approximation may fail under certain circumstances, as experimental [1] and theoretical [2] studies suggest. In such cases, the correct description of the molecule’s excited states becomes of vital importance for the comprehension of the ongoing chemical processes. Accordingly, we will discuss the role of static correlation for this model system by comparing state-of-the-art MRCI and GGA-DFT calculations.

[1] R. Burgert et al., Science 319, 438 (2008).

[2] C. Carbogno et al., Phys. Rev. Lett. 101, 096104 (2008).