1. State Key Laboratory of Crystal Materials Institute of Crystal Materials Shandong University Jinan Shandong 250100 P. R. China
2. Beijing Key Laboratory of Energy Conversion and Storage Materials College of Chemistry Beijing Normal University Beijing 100875 P. R. China
3. School of Physics Shandong University Jinan Shandong 250100 P. R. China
4. School of Civil Engineering Shandong Jiaotong University Jinan Shandong 250300 P. R. China