1. Institute of Physics; Chinese Academy of Sciences; Beijing 100190 China
2. Centre for Advanced Structural Materials Department of Mechanical and Biomedical Engineering; City University of Hong Kong; Hong Kong China
3. Beijing Institute of Nanoenergy and Nanosystems; Chinese Academy of Sciences; National Center for Nanoscience and Technology (NCNST); Beijing 100083 China
4. College of Environmental and Energy Engineering; Beijing University of Technology; Beijing 100124 China
5. Beijing Computational Science Research Center; Beijing 100193 China
6. School of Material Science and Engineering; Georgia Institute of Technology; Atlanta GA 30332-0245 USA