1. Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India
2. Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
3. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
4. Department of Materials Science and Engineering, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110016, India