1. Key Laboratory of UV-Emitting Materials and Technology of Ministry of Education, School of Physics, Northeast Normal University 1 , Changchun 130024, China
2. Department of Physics, Rutgers University 2 , Newark, New Jersey 07102, USA
3. College of Science, Shenyang University of Chemical Technology 3 , Shenyang 110142, China
4. Key Laboratory of Material Simulation Methods and Software of Ministry of Education and State Key Laboratory of Superhard Materials, College of Physics, Jilin University 4 , Changchun 130012, China