Ion-water cluster free energy computer simulation using some of most popular ion-water and water-water pair interaction models

The bicanonical Monte-Carlo method allows effective computer simulation of free energy, entropy as well as internal energy of ion molecular clusters. The advantages of this method have been exploited to test how much adequately frequently applied pair interaction models reproduce not only energetics, but also statistical properties of the investigated ion-water clusters. In present paper, the series of reproductions of mass spectroscopy data on stepwise binding Gibbs energy, enthalpy and entropy of Ion(H2O)n, n = 1 ÷ 6 clusters for a set of monovalent ions has been carried out with the help of bicanonical Monte-Carlo technique. Each reproduction from the series has been performed using one of pair interaction ion-water plus water-water models, the experimental data on free energy, entropy as well as internal energy of ion molecular clusters. Based on the result of the simulations, the quantitative analysis of the investigated pair interaction models accuracy has been accomplished. The accuracy of the pair interaction ion-water plus water-water models has been compared with the accuracy of the one of polarizable models taking into account polarization of ions and water molecules explicitly.