1. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139, United States
2. Center for Theoretical Physics
and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
3. Lehrstuhl für Theoretische
Chemie, Ruhr-Universität Bochum,
44780 Bochum, Germany