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 calculat ions have been performed on the extended simple point charge (SPC/E) m odel water to understand the effects of pressure on its structural and dynamical properties. The effect of pressure is to increase the prese nce of interstitial water molecules, which is shown to be responsible for the experimentally observed increase in the first x-ray diffractio n peak and a broadening of the (OOO) over cap bond angle distribution. These structural changes lead to weaker hydrogen bonding and the obse rved minimum in the rotational correlation time as a function of press ure. The weak maximum in the measured translational diffusion coeffici ent at around 1.5 kbar was not reproduced. The temperature of the dens ity maximum was estimated to occur at 245+/-4 K, which suggests that s tructural changes with increasing pressure and decreasing temperature are not quantitatively reproduced by the SPC/E model. (C) 1997 America n Institute of Physics. [S0021-9606(97)51644-8].