1. Institute of Physical Chemistry, University of Vienna, Währingerstrasse 42, A-1090 Wien, Austria
2. Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8−10, A-1040 Wien, Austria
3. Center for Computational Materials Science, University of Vienna, Sensengasse 8/7, A-1090 Wien, Austria
4. Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria