Molecular Dynamics of High-Pressure Liquid Water: Going from Ambient to Near-Critical Temperatures

Abstract

The properties of high-pressure liquid water were investigated along the isobar of 25 MPa and in the temperature range 298.15-623.15 K using classical molecular dynamics simulations. Particular attention has been given to the changes in the local structural and related dynamic properties of liquid water. The results obtained have revealed noticeable changes in the shape of the calculated radial distribution functions, as well as the existence of local extrema or crossovers in several structural descriptors and entropic quantities at temperatures around 423.15 K and 498.15 K, where also significant changes in the hydrogen bond network of liquid water have also been observed. The temperature dependence of translational, reorientational, and hydrogen bond dynamics of liquid water has also been investigated by calculating the translational self-diffusion and the corresponding O-H vector Legendre reorientational correlation times and hydrogen bond lifetimes. The corresponding activation energies for each investigated relaxation process have also been presented and discussed.