CALCULATION OF EFFECTIVE INTERACTION POTENTIALS FROM RADIAL-DISTRIBUTION FUNCTIONS - A REVERSE MONTE-CARLO APPROACH

An approach is presented to solve the reverse problem of statistical m echanics: reconstruction of interaction potentials from radial distrib ution functions. The method consists of the iterative adjustment of th e interaction potential to known radial distribution functions using a Monte Carlo simulation technique and statistical-mechanics relations to connect deviations of canonical averages with Hamiltonian parameter s. The method is applied to calculate the effective interaction potent ials between the ions in aqueous NaCl solutions at two different conce ntrations. The reference ion-ion radial distribution functions, calcul ated in separate molecular dynamics simulations with water molecules, are reproduced in Monte Carlo simulations, using the effective interac tion potentials for the hydrated ions. Application of the present meth od should provide an effective and economical way to simulate equilibr ium properties for very large molecular systems (e.g., polyelectrolyte s) in the presence of hydrated ions, as well as to offer an approach t o reduce a complexity in studies of various associated and aggregated systems in solution.