1. State Key Laboratory of Superhard Materials Department of Materials Science and Key Laboratory of Automobile Materials MOE Jilin University Changchun 130012 China
2. Department of Materials Science and Engineering Jilin Jianzhu University Changchun 130118 China
3. International Center for Computational Methods and Software College of Physics Jilin University Changchun 130012 China
4. Department of Physics and Astronomy University of Nevada, Las Vegas Las Vegas NV 89154 USA