(329d) From Structure to Thermodynamics With Local Molecular Field Theory

A fundamental problem in statistical mechanics is the development of accurate and efficient means to calculate free energies. A novel “bottom-up” approach to the calculation of thermodynamic properties is described, in which free energies of systems containing long-ranged interactions are obtained by integration over the structure of an appropriately chosen purely short-ranged “mimic system”, a fact that is especially advantageous when long-ranged Coulomb interactions are present. Local molecular field (LMF) theory of nonuniform fluids is employed to obtain an accurate description of the structure in the short ranged system, then LMF ideas are extended in a very simple way to determine contributions to the free energy from the long ranged interactions using only the structural properties of the mimic system. After introducing this LMF theory-based framework, its accuracy will be demonstrated on several problems of interest, including hydration free energies of hydrophobic solutes and ions, simple alchemical transformations, and general potentials of mean force.