1. P. H. Poole is in the Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7, Canada. ,
2. T. Grande is in the Department of Inorganic Chemistry, Norwegian University of Science and Technology, N-7034 Trondheim, Norway.
3. C. A. Angell and P. F. McMillan are in the Department of Chemistry, Arizona State University, Tempe, AZ 85287, USA.