1. Key Laboratory of Computational Physical Sciences (Ministry of Education) Institute of Computational Physical Sciences State Key Laboratory of Surface Physics and Department of Physics Fudan University Shanghai 200433 China
2. Shanghai Qi Zhi Institute Shanghai 200232 China
3. Physics Department and Institute for Nanoscience and Engineering University of Arkansas Fayetteville AR 72701 USA
4. Department of Physics and Information Technology Baoji University of Arts and Sciences Baoji 721016 China