Density and temperature effect on hydrogen-bonded clusters in water - MD simulation study

Abstract

Molecular dynamics NVE simulations have been performed for five thermodynamic states of water including ambient, sub-and supercritical conditions. Clustering of molecules via hydrogen bonding interaction has been studied with respect to the increasing temperature and decreasing density to examine the relationship between the extent of hydrogen bonding and macroscopic properties. Calculations confirmed decrease of the average number of H-bonds per molecule and of cluster-size with increasing temperature and decreasing density. In the sub-and supercritical region studied, linear correlations between several physical quantities (density, viscosity, static dielectric constant) and the total engagement of molecules in clusters of size k > 4, P _k>4, have been found. In that region there was a linear relationship between P _k>4 and the average number of H-bonds per water molecule. The structural heterogeneity resulting from hydrogen bonding interactions in low-density supercritical water has been also discussed.