1. Department of Physics and Multi-scale Technology Institute, Michigan Technological University, Houghton, Michigan 49931
2. Fachbereich C- Theoretische Chemie, Universität Wuppertal, Gauss Str. 20, D-42097 Wuppertal, Germany
3. US Army Research Laboratory, Weapons and Materials Research Directorate, ATTN: RDRL-WM, Aberdeen Proving Ground, Maryland 21005-5069