1. Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
2. Faculty of Chemistry, North-east Normal University, Changchun, 130024, P. R. China
3. Department of Chemistry and Applied Biosciences - Computational Science, ETH Zürich, Via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland