1. College of Chemistry and Chemical Engineering Jiangxi Normal University Nanchang 330022 P. R. China
2. Laboratory of Theoretical and Computational Nanoscience National Center for Nanoscience and Technology of China Beijing 100190 P. R. China
3. State Key Laboratory of Information Security, Institute of Information Engineering Chinese Academy of Sciences Beijing 100195 P. R. China
4. School of Cyber Security University of Chinese Academy of Sciences Beijing 100195 P. R. China