1. Center for Computational Quantum Chemistry, South China Normal University, Guangzhou 510631, P. R. China
2. College of Science, Northwest A&F University, Yanlin, Shanxi 712100, P. R. China
3. Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, P. R. China
4. Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA