Selection of a quantum-chemical method and basis set for optimization of the complex ion Cu(H2O)+

Calculations of the open-shell van der Waals complex Cu(H₂O)⁺ were carried out at 15 theoretical levels basing on the DFT theory in its variants B3LYP and BLYP. Five types of basis function were used (3-21G*, 3-21G**, 6-31G(d,p), 6-311G(d,p) and CEP-4G) each combined with one (+) or two (++) diffuse functions. The aim of the research was to find out the most accurate combination of method and basis set which predicts structural, energetic and vibration parameters closest to the experimentally found ones. Several experimental parameters were used as reference values.