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. Chem. 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.