1. Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Material Science and Engineering, Northeastern University 1 , Shenyang 110819, China
2. Department of Physics, Freie Universität Berlin 2 , Berlin 14195, Germany
3. State Key Laboratory of Superhard Materials, College of Physics, Jilin University 3 , Changchun 130012, China