Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Ave., Athens 116 35, Greece, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan, and SORST, Japan Science and Technology Agency, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501, Japan(At 2008-03-18)
