1. Scuola Internazionale Superiore di Studi Avanzati and INFM - DEMOCRITOS National Simulation Center, Via Beirut 2-4, 34014 Trieste, Italy, Laboratory of Computational Chemistry and Biochemistry, Federal Institute of Technology - EPFL, 1015 Lausanne, Switzerland, and Nanochemistry Research Institute, Curtin University of Technology, P.O. Box U 1987, Perth WA 6845, Australia