Evaluation of the performance of GAFF and CGenFF in the prediction of liquid-vapor saturation properties of naphthalene derivatives

We examine the performance of the general AMBER force field (GAFF) and the CHARMM general force field (CGenFF) within the context of capturing the liquid-vapor saturation properties of naphthalene derivatives. Molecular simulation is employed to construct phase diagrams for naphthalene, tetralin, trans-decalin, quinolone, 1-methylnaphthalene, 1-naphthol, indole, benzo[b]furan, and benzo[b]thiophene over a range of temperatures that spans from room temperature to the critical point. A general histogram-based approach introduced by Rane and co-workers (J. Chem. Theory Comput. 2013, 9, 2552) is used to calculate saturated densities, vapor pressures, and enthalpies of vaporization. Results for GAFF and CGenFF are compared to experimental data, available correlations, and literature results for the transferable potentials for phase equilibria force field (TraPPE). GAFF and CGenFF provide reasonable descriptions for the saturation properties of the naphthalene derivatives studied. Specifically, GAFF and CGenFF capture the critical temperature to within average errors of 5.6 and 6.3%, respectively, and the boiling temperature to within average errors of 4.0 and 4.4%, respectively. The models generally produce estimates of the critical temperature and boiling temperature that are low relative to experiment. The two models provide a relatively consistent description of the six molecules studied containing two fused six-membered rings, whereas their description of the three molecules examined containing fused five- and six-membered rings often differs appreciably. In terms of an overall comparison, our results do not indicate that one force field clearly outperforms the other.