Temperature Dependence of the Hydrophobic Hydration and Interaction of Simple Solutes: An Examination of Five Popular Water Models

TL;DR

This study compares five popular water models through MD simulations to understand how temperature affects hydrophobic hydration and interactions, revealing model-dependent differences and the importance of water structure in these phenomena.

Contribution

It provides a systematic analysis of temperature-dependent hydrophobic effects across multiple water models, highlighting the role of density and structure in modeling accuracy.

Findings

TIP5P closely matches experimental hydration data at low temperatures

Hydrophobic interactions vary significantly with temperature and model used

Density rescaling explains differences between models and real water

Abstract

We examine five different popular rigid water models (SPC, SPCE, TIP3P, TIP4P and TIP5P) using MD simulations in order to investigate the hydrophobic hydration and interaction of apolar Lennard-Jones solutes as a function of temperature in the range between $275 {K}$ and $375 {K}$. For all investigated models and state points we calculate the excess chemical potential for the noble gases and Methane.All water models exhibit too small hydration entropies, but show a clear hierarchy. TIP3P shows poorest agreement with experiment whereas TIP5P is closest to the experimental data at lower temperatures and SPCE is closest at higher temperatures. A rescaling procedure inspired by information theory model of Hummer et al. ({\em Chem.Phys.}258, 349-370 (2000)) suggests that the differences between the different models and real water can be explained on the basis of the density curves at constant pressure. In addition, the models that give a good representation of the water structure at ambient conditions (TIP5P, SPCE and TIP4P) show considerably better agreement with the experimental data than SPC and TIP3P. We calculate the hydrophobic interaction between Xenon particles directly from a series of 60 ns simulation runs.We find that the temperature dependence of the association is related to the strength of the solvation entropy. Nevertheless, differences between the models seem to require a more detailed molecular picture.The TIP5P model shows by far the strongest temperature dependence.The suggested density-rescaling is also applied to the Xenon-Xenon contact-pair configuration, indicating the presence of a temperature where the hydrophobic interaction turns into purely repulsive.The predicted association for Xenon in real water suggest the presence a strong variation with temperature.