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Lecture Volker Staemmler


15 juli 2005 FWN-Building 5116.0107, Nijenborgh 4, 9747 AG, Groningen
Speaker:Prof. Volker Staemmler
Affiliation:Ruhr-Universitaet Bochum, Germany
Title:Magnetic exchange coupling in binuclear Co and Fe complexes
Date:Fri Jul 15, 2005
Location:FWN-Building 5116.0107
Host:R. Broer
Telephone:+31 50 363 4374


The magnetic exchange coupling between local spins in bridged transition metal complexes is treated with wave function based quantum chemical ab initio methods. The calculations are performed in several steps with increasing complexity. First, the magnetic orbitals involved are generated in a restricted open-shell Hartree-Fock (ROHF) or a complete active space SCF (CASSCF) calculation. Next, these orbitals are used in a configuration interaction (CI) treatment to describe the excited charge transfer configurations which are responsible for the antiferromagnetic exchange coupling. Spin-orbit coupling (SOC) and Zeeman splittings in a finite external magnetic field can also be included in this CI. Finally, multi-configuration CI or coupled cluster schemes are employed to improve the accuracy of the results. The results of the calculations are used to extract the parameters in the conventional spin Hamiltonian (exchange coupling constants J, g-factors, zero field splitting parameters D,E etc. or to evaluate directly the temperature dependence of the magnetic susceptibility ?(T). In the present talk, this treatment is applied to two different systems: 1. Binuclear Co(II) complexes and CoO: The isolated Co(II) ion possesses a 4F ground state with an overall spin-orbit splitting of about 1000 cm ?1, which is of the same size as ligand field effects. 2. Iron-sulfur clusters, in particular [2Fe2S] ferredoxins: These biologically important clusters possess a complicated spin structure.
Laatst gewijzigd:22 oktober 2012 14:31