Theoretical Investigation of Small Alkali Cation−Molecule Clusters:  A Model Potential Approach

We present here a model potential study of the microsolvation of alkali cations M + (M = Na, K, Rb, Cs) in various solvents (water, methanol, dimethyl ether (DME)). The potential energy surfaces (PES) are explored with the Monte Carlo growth method (MCGM) to find the most significant equilibrium structures of M + −(solvent) n clusters ( n = 2, 4). The structures as well as the binding energies are favorably compared to the best ab initio calculations found in the literature and to experimental results. This good agreement is only obtained if we take into account the anisotropy of the polarizability tensor for the solvent molecule. Under these conditions, the atomic parameters included in our model potential framework are found to be transferable from water to methanol and DME. An analysis of the different physical components of the interaction energy shows that the only important n-body term for the description of these systems is the polarization one.