Molecular Dynamics Simulation Study for Shear Viscosity of Water at High Temperatures using SPC/E Water Model

Abstract

In the past decades, many classical force fields for molecular simulations on water have been developed. A review article in 2002 indicates that there are 46 water models, which were classified as rigid, flexible, and polarizable models. The most popular water models the TIP3P (transferable intermolecular potential 3P) (original and modified), SPC (simple point charge) (original and refined), and SPC/E (extended SPC) can be described as effective rigid pair potentials composed of Lennard-Jones and Coulombic terms. Recent studies using a rigid non-polarizable water model, TIP4P/2005, reported an impressive performance for a wide variety of properties and thermodynamic conditions. Our interest in this study concentrated on the shear viscosity  of the bulk water. The experimental value for shear viscosities of pure water have been measured to be 0.896 cP at 298 K and 0.854 cP at 300 K. Shear viscosities evaluated using molecular dynamics (MD) simulations have been reported: 0.31 and 0.321 cP for TIP3P, 0.47 and 0.494 cP for TIP4P, 0.699 cP for TIP5P, 0.64, 0.65, 0.67, 0.68, 0.72, and 0.729 cP for SPC/E (the results for TIP3P and SPC/E correspond to temperatures slightly above 300 K except Ref. 24 for 298 K), and 0.855 and 0.83 cP for TIP4P/2005. Though TIP4P/2005 performs quite well, the prediction from SPC/E is somewhat acceptable at room temperatures and this water model has been widely used. However, MD results for shear viscosity at high temperatures are rarely found in the literature. In this study, we utilize the GreenKubo (GK) formula for the calculation of shear viscosities of SPC/E water using MD simulations over the range of temperatures 300 to 550 K. The primary goal of this study is to compare shear viscosities of water with the experimental measures at high temperatures and to examine the temperature dependence of shear viscosity of SPC/E water.