1. Theoretical Chemistry Section, Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India and Homi Bhabha National Institute, Mumbai 400094, India
2. Chemistry and Biochemistry Department, North Dakota State University, Fargo, North Dakota 58108-6050, USA
3. Quantum Theory Project, Departments of Chemistry and of Physics, University of Florida, Gainesville, Florida 32611, USA