1. Université
de Genève,
Faculté des Sciences, Quai E. Ansermet 30, CH-1211 Genève
4, Switzerland
2. Department
of Chemistry - Ångström,
The Theoretical Chemistry Programme, Uppsala University, P.O. Box
518, SE-751 20 Uppsala, Sweden
3. CSCS Swiss National Supercomputing
Centre, Via Trevano 131, CH-6900 Lugano, Switzerland