1. Center for Crystal Research and Development; Key Laboratory of Functional Crystals and Laser Technology; Technical Institute of Physics and Chemistry; Chinese Academy of Sciences; Beijing 100190 P. R. China
2. University of Chinese Academy of Sciences; Beijing 100049 P. R. China
3. College of Chemistry and Molecular Engineering; Peking University; Beijing 100871 P. R. China
4. Centre for High Pressure Research; School of Physics Bharathidasan University; Tiruchirapalli 620024 India