1. Centre for Theoretical Chemistry and PhysicsThe New Zealand Institute for Advanced StudyMassey University Auckland 0632 Auckland New Zealand
2. Mulliken Center for Theoretical ChemistryUniversity of Bonn Beringstr. 4 53115 Bonn Germany
3. University of ViennaFaculty of Physics and Center for Computational Materials Sciences Sensengasse 8/12 1090 Wien Austria