Influence of cut-off truncation and artificial periodicity of electrostatic interactions in molecular simulations of solvated ions:A continuum electrostatics study

摘要

A new algorithm relying on finite integration is presented that solves the equations of continuum electrostatics for truncated (and possibly reaction-field corrected) solute-solvent and solvent-solvent interactiosn under either nonperiodic or periodic boundary conditions.After testing and validation by comparison with existing methods,the algorithm is applied to investigate the effect of cut-off truncation and artificial periodity in explicit-solvent simulations of ionic solvation and ion-ion interactions.Both cut-off truncation and artificial periodity significantly alter the polarization around a spherical ion and thus,its solvation free energy.The nature and magnitude of the two perturbations are analyzed in details,and correction terms are proposed for both effects.Cut-off truncation is also shown to induce strong alterations in the potential of mean force for ion-ion interaction.These observations help to rationalize artifacts previously observed in explicit-solvent simulations,namely spurious features in the radical distribution functions close to the cut-off distance and alterations in the relative stabilities of contact,solvent-separated and free ion pairs.