1. Dipartimento di Scienze Chimiche, Università degli Studi di Trieste, via L. Giorgieri 1, I-34127 Trieste, Italy and Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, N-0315, Blindern, Norway
2. Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway