1. Centre for Computational Science, Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London WC1H 0AJ, U.K., Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, U.K., Department of Materials, Queen Mary, University of London, Mile End Road, London E1 4NS, U.K., and Regional Research Laboratory, Trivandrum 695 019, India