1. Institute of Theoretical Chemistry, College of Chemistry, Jilin University, 130023 Changchun, P. R. China
2. Institute of Chemistry Chinese Academy of Sciences, 100190 Beijing, P. R. China
3. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV1067, Latvia
4. School of Materials and Physics, China University of Mining and Technology, 221116 Xuzhou, P. R. China
5. College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, 210046 Nanjing, P. R. China