1. Eduard-Zintl Institute for Inorganic and Physical Chemistry, TU Darmstadt, Darmstadt 64287, Germany
2. University of California at Berkeley, College of Chemistry and QB3, Berkeley, California 94720, USA
3. International Tomography Center, Siberian Branch of the Russian Academy of Sciences, and Novosibirsk State University, Novosibirsk 630090, Russia