SIMULATED ANNEALING ON FREE-ENERGY SURFACES BY A COMBINED MOLECULAR-DYNAMICS AND MONTE-CARLO APPROACH

A method is presented for sampling coupled potent al energy surfaces and selecting the one with the most favorable free energy. Cartesian coordinates and chemical composition are treated as independent variables of the system, and simulated annealing is used to optimize in coordinate and composition spaces to produce a minimum free energy subensemble. Molecular dynamics is used to sample in the Cartesian dimensions, and a Monte Carlo approach is used to sample in the chemical dimensions. The method has been applied to selecting the solute with the most favorable solvation energy for the well-studied system of bromide and chloride. The method is able to distinguish the more soluble ion more quickly than a full calculation of the free energy difference between the solutes.