1. National Research Center Kurchatov Institute, Moscow 123182, Russia
2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
3. Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, California 94720, USA
4. Leibniz-Institut für Kristallzüchtung, 12489 Berlin, Germany
5. VITCON Projectconsult GmbH, 07745 Jena, Germany
6. Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany