Hamburg 2009 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 15: Theorie: Quantenchemie
MO 15.1: Vortrag
Mittwoch, 4. März 2009, 16:45–17:00, VMP 6 HS-F
The d-Hamiltonian: A new approach for evaluating optical spectra of transition metal complexes — •Stefan Lebernegg, Georg Amthauer, and Michael Grodzicki — FB Materialforschung und Physik, Universität Salzburg, Hellbrunnerstraße 34, A-5020 Salzburg
The full multi-centre molecular Hamiltonian in local density approximation for a mononuclear transition metal complex is transformed into a single-centre Hamiltonian explicitly including overlap, covalency and ligand-field effects. The orbital interactions of the metal d-orbitals with the ligand orbitals appear as a repulsive pseudopotential yielding the dominant contribution to the ligand-field splitting. This repulsive pseudopotential exhibits the same angular dependence as the electrostatic potential from the ligands entering the Hamiltonian of ligand-field theory. For this reason, ligand-field theory very often yields the correct splitting pattern of the d-orbitals. The radial part, however, is considerably different from the simple expression of ligand-field theory. In particular, there is no general theoretical justification for a R−5-dependence of the ligand-field splitting even for complexes of cubic symmetry. The reliability and capability of this new approach is demonstrated by calculating the d-orbital splitting pattern for a number of selected systems. Therefore the d-Hamiltonian is a new and versatile tool for interpreting and evaluating optical spectra (as well as magnetic properties) of transition metal complexes.