[1] Tech Univ Munich, Lehrstuhl Theoret Chem, D-85747 Garching, Germany
[2] Univ Barcelona, Dept Quim Fis, E-08028 Barcelona, Spain
[3] Univ Milan, Ist Nazl Fis Mat, Dipartimento Sci Mat, I-20126 Milan, Italy
[4] Jackson State Univ, Dept Chem, Jackson, MS 39217 USA
[5] Univ Stockholm, S-11385 Stockholm, Sweden
[6] Univ Turin, Dipartimento Chim Inorgan Chim Fis & Chim Mat, I-10125 Turin, Italy