1. Department of Physical and Organic Chemistry, Institute Jožef Stefan, Jamova 39, SI-1000 Ljubljana, Slovenia, Centre for Molecular Modeling, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia, Department of Process Engineering and Environmental Technology, Management Center Innsbruck, Egger-Lienz Strasse 120, A-6020 Innsbruck, Austria, and Institut für Physikalische und Theoretische Chemie der Universität Bonn, Wegelerstrasse 12, 53115 Bonn, Germany