1. Chemistry Department, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, Department of Physics and Chemistry, University of Southern Denmark, Odense University, Campusvej 55, 5230 Odense M, Denmark, Atomate Corporation, 2665-D Park Center Drive, Simi Valley, California 93065, and Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802