1. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
2. Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
3. The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-632, United States
4. Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
5. Departamento de Física, Universidad San Francisco de Quito, Quito 170901, Ecuador
6. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510006, People’s Republic of China