1. Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, D-81377 München, Germany
2. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
3. Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, D-81377 München, Germany
4. Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany