1. a Department of Physical Chemistry, Faculty of Sciences , Comenius University , Mlynska dolina, SK-842 15 , Bratislava , Slovakia
2. b Department of Quantum Chemistry , Institute of Chemistry, Nicolas Copernicus University , 7, Gagarin St., PL-87 100 , Toruń , Poland
3. c Department of Theoretical Chemistry, Chemical Centre , University of Lund , PO Box 124, S-221 00 , Lund , Sweden