1. Center for Combustion Energy, Tsinghua University, Beijing 100084, P. R. China
2. School of Aerospace Engineering, Tsinghua University, Beijing 100084, P. R. China
3. Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
4. School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China