Combinedab initio/empirical approach for optimization of Lennard-Jones parameters

Abstract

Obtaining accurate Lennard–Jones (L-J) parameters is a vital part of the optimization of empirical force fields due to their significant contribution to condensed-phase properties. We present a novel approach to optimize L-J parameters via the use of ab initio data on interactions between rare gas atoms and model compounds combined with the reproduction of experimental pure solvent properties. Relative values of ab initio minimum interaction energies and geometries between helium or neon and model compounds were used to optimize the relative magnitude of the L-J parameters. Absolute values of the L-J parameters were determined by reproducing experimental heats of vaporization and molecular volumes for pure solvents. Application of the approach was performed on methane, ethane, and propane. Free energies of aqueous solvation and butane pure solvent and aqueous solvation calculations were used to test the developed L-J parameters. The new alkane parameters are similar or improved as compared with current empirical force field parameters with respect to experimental pure solvent properties and free energies of aqueous solvation. Also included is a description of the internal portion of the force field. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 334–348, 1998