The Cu+–H2O interaction potential and its application to the study of [Cu(H2O)n]+ clusters at different temperatures

Abstract

An analyitcal pair potential for the interaction of Cu⁺ ion with H₂O has been obtained by fitting to quantum-mechanically calculated energies of the monohydrate Cu⁺–H₂O. This analytical potential and Clementi's MCY potential for the H₂O–H₂O interaction have been used in the pairwise approximation to study [Cu(H₂O)_n]⁺ clusters, with n= 6, 8, 10, 15 and 20. This study has been performed at T= 0 K by energy minimization and at T= 50, 298 and 500 K using Monte Carlo techniques, in order to assess the effect of thermal motion. A detailed analysis of the interaction energies, the resulting radial distribution functions and the corresponding running coordination number leads to the prediction of a coordination number of six for the first hydration shell of the Cu⁺ ion. In this first shell the water molecules have an octahedral structure, which is slightly distorted when the temperature is increased. The reliability of these results and their validity at infinite dilution are discussed.