1. Limburgs Universitair Centrum, Department SBG, Universitaire Campus, B-3590 Diepenbeek, Belgium, and University of Antwerp (UIA), Institute for Materials Science, Department of Chemistry, Universiteitsplein 1, B-2610 Wilrijk, Belgium
2. San Diego Supercomputer Center, P. O. Box 85608, San Diego, California 92186-9784