1. Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University 1 , Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
2. Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU) 2 , D-81377 Munich, Germany
3. Max Planck Institute for Solid State Research 3 , 70569 Stuttgart, Germany