Correcting for electrostatic cutoffs in free energy simulations: Toward consistency between simulations with different cutoffs

The use of electrostatic cutoffs in calculations of free energy differences by molecular simulations introduces errors, Even though both solute-solvent and solvent-solvent cutoffs are known to create discrepancies, past efforts have mostly been directed toward correcting for the solute-solvent cutoffs. In this work, an approach based on the generalized reaction field formalism is developed to correct for the solvent-solvent cutoff errors as well. It is shown using a series of simulations that when the cutoff lengths are significantly smaller than the half unit cell size, and the solute-solvent cutoff is not much larger than the solvent-solvent cutoff, the new algorithm is able to yield better agreement among simulations employing different truncation lengths. (C) 1998 American Institute of Physics.