The effects of pressure on structural and dynamical properties of associated liquids: Molecular dynamics calculations for the extended simple point charge model of water

Constant temperature and constant pressure molecular dynamics calculations have been performed on the extended simple point charge (SPC/E) model water to understand the effects of pressure on its structural and dynamical properties. The effect of pressure is to increase the presence of interstitial water molecules, which is shown to be responsible for the experimentally observed increase in the first x-ray diffraction peak and a broadening of the (OOO) over cap bond angle distribution. These structural changes lead to weaker hydrogen bonding and the observed minimum in the rotational correlation time as a function of pressure. The weak maximum in the measured translational diffusion coefficient at around 1.5 kbar was not reproduced. The temperature of the density maximum was estimated to occur at 245+/-4 K, which suggests that structural changes with increasing pressure and decreasing temperature are not quantitatively reproduced by the SPC/E model. (C) 1997 American Institute of Physics. [S0021-9606(97)51644-8].