A reexamination of the hydrophobic effect: Exploring the role of the solvent model in computing the methane-methane potential of mean force

Molecular dynamics simulations are used to examine the role of explicit electronic polarization on the computed potential of mean force (PMF) for methane-methane association in water. Calculations were performed using the same simulation protocol with;three different water models: the TIP3P model [J. Chem. Phys. 79, 926 (1983)], the TIP4P model [J. Chem. Phys. 79, 926 (1983)], and a polarizable version of the TIP4P model [J. Chern, Phys. 95, 7556 (1988)]. By computing the PMF for methane-methane association in three different water models, we are able to isolate effects that arise from the inherent structure of the water model versus those that are a result of adding explicit electronic polarization to the water model. We observe links between the structuring of the solvent and the computed PMF for methane-methane association. These results suggest that for the water models used, the inherent structure of the water model has a greater effect on the methane-methane PMF than does solvent polarizability. (C) 1997 American Institute of Physics.