1. Institute of Applied Physics; Vienna University of Technology; Wiedner Hauptstrasse 8-10/134 1040 Vienna Austria
2. Interdisciplinary Center for Molecular Materials and Computer-Chemistry-Center; Friedrich-Alexander-University Erlangen-Nürnberg; Nägelsbachstrasse 25 91052 Erlangen Germany
3. Materials Science and Technology Division; Oak Ridge National Laboratory; Oak Ridge Tennessee 37831 USA