1. Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, MN 55455
2. Current address: Departments of Chemistry and Physics, Mercyhurst College, 501 East 38th Street, Erie, PA 16546
3. Eastman Kodak Company, Rochester, NY 14650
4. Laboratoire de Physico-Chimie Theorique, Universite de Bordeaux 1, 351 Cours de la Liberation, 33405 Talence Cedex, France