1. College of Physics/State Key Laboratory of Superhard Materials, Jilin University, 130012, Changchun, People’s Republic of China
2. Division of Inorganic and Structural Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm, Sweden
3. Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
4. Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
5. Institute for Physics of Condensed Matter, TU Braunschweig, D-38106 Braunschweig, Germany