Electrostatic potentials and free energies of solvation of polar and charged molecules

摘要

Theories of solvation free energies often involve electrostatic potentials atthe position of a solute charge. Simulation calculations that apply cutoffs andperiodic boundary conditions based on molecular centers result incenter-dependent contributions to electrostatic energies due to a systematicsorting of charges in radial shells. This sorting of charges induces asurface-charge density at the cutoff sphere or simulation-box boundary thatdepends on the choice of molecular centers. We identify a simple solution thatgives correct, center-independent results, namely the radial integration ofcharge densities. Our conclusions are illustrated for a Lennard-Jones solute inwater. The present results can affect the parameterization of force fields.