1. Sandia National Laboratories, Advanced Materials Laboratory, MS 1349, 1001 University Boulevard SE, Albuquerque, New Mexico 87106, and Sandia National Laboratories, MS 1407, P.O. Box 5800, Albuquerque, New Mexico 87185
2. Department of Chemistry, X-ray Diffraction Laboratory, University of CaliforniaIrvine, Irvine, California 92717