ON FINITE-SIZE CORRECTIONS TO THE FREE-ENERGY OF IONIC HYDRATION

Efforts to compare thermodynamic predictions of simulations with exper iment have been thwarted by the approximations used in modeling the lo ng-range electrostatic interactions. In a recent article Hummer et al. proposed an explicit formula that accounts for most of the finite-siz e effect in simulations of ion charging using periodic boundary condit ions, In this Letter we have verified the numerical results of Hummer et al, and we provide a simple theoretical argument that explains why the solvent polarization free energy contains a contribution that larg ely cancels the lattice self-energy, The cancellation depends on the f act that the solvent is a high dielectric, We propose a finite size co rrection formula that can be applied in both the low and high dielectr ic limits.