1. State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, P. R. China
2. Department of Radiotherapy, The Second Hospital of Jilin University, No. 218 Ziqiang Street, Changchun 130041, P. R. China
3. College of Science, Liaoning University of Technology, Jinzhou, 121000, P. R. China