1. Laboratory
of Theoretical Chemistry, Unit of Theoretical and Structural Physical
Chemistry, Namur Institute of Structured Matter, University of Namur, Rue de Bruxelles, 61, 5000 Namur, Belgium
2. Department
of Physics, University of Utah, Salt Lake City, Utah 84112, United States
3. Quantum
Theory Project, University of Florida, Gainesville, Florida 32611, United States