1. Shubnikov Institute of Crystallography, Russian Academy of Sciences, 59 Leninskii Prospect, Moscow 117333, Russia
2. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, USA
3. Mineralogisch–Petrologisches Institut und Museum der Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany