1. Mulliken Center for Theoretical Chemistry; University of Bonn; Beringstrasse 4+6 53115 Bonn Germany
2. Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
3. School of Chemistry and Chemical Engineering; Queen's University of Belfast; Belfast BT7 1NN UK
4. Institute of Inorganic Chemistry; TU Bergakademie Freiberg; 09599 Freiberg Germany
5. Max Planck Institute for Chemical Physics of Solids; Nöthnitzer Strasse 40 01187 Dresden Germany