1. Department of Chemistry, University of Jyväskylä, P.O. Box 35, Jyväskylä, Finland
2. Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
3. Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, United Kingdom
4. Institut für Theoretische Physik, Goethe-Universität, Frankfurt am Main 60438, Germany
5. Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1, Canada