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 differ ences by molecular simulations introduces errors, Even though both sol ute-solvent and solvent-solvent cutoffs are known to create discrepanc ies, past efforts have mostly been directed toward correcting for the solute-solvent cutoffs. In this work, an approach based on the general ized reaction field formalism is developed to correct for the solvent- solvent cutoff errors as well. It is shown using a series of simulatio ns that when the cutoff lengths are significantly smaller than the hal f unit cell size, and the solute-solvent cutoff is not much larger tha n the solvent-solvent cutoff, the new algorithm is able to yield bette r agreement among simulations employing different truncation lengths. (C) 1998 American Institute of Physics.