1. Institute
of Solid State Physics, Friedrich-Schiller-University Jena, Max-Wien-Platz
1, 07743 Jena, Germany
2. Bremen
Center for Computational Materials Science (BCCMS), University of Bremen, Am Fallturm 1, 28359 Bremen, Germany
3. Institute
of Solid State Physics, University of Bremen, Otto-Hahn-Allee NW1, 28359 Bremen, Germany
4. Institute
of Physics and Material Science Center, Philipps-University Marburg, Renthof 5, 35032 Marburg, Germany