Thermodynamic and structural properties of liquid water around the temperature of maximum density in a wide range of pressures: A computer simulationstudy with a polarizable potential model
P. Jedlovszky et R. Vallauri, Thermodynamic and structural properties of liquid water around the temperature of maximum density in a wide range of pressures: A computer simulationstudy with a polarizable potential model, J CHEM PHYS, 115(8), 2001, pp. 3750-3762
Computer simulations of liquid water have been performed with the polarizab
le Brodholt-Sampoli-Vallauri (BSV) potential model at several temperatures
around the temperature of maximum density (TMD) in the entire pressure rang
e in which such a density maximum exists in thermodynamically stable liquid
water. The temperature and pressure dependence of the thermodynamic and st
ructural properties has been analyzed on the basis of these simulations. We
find that the BSV model reproduces most of the important thermodynamic fea
tures of water in this temperature and pressure range. The BSV model is als
o found to reproduce another of the anomalous properties of liquid water, i
.e., the isothermal compressibility goes through a minimum when the tempera
ture is increased. On the other hand, it is found that above the TMD the de
nsity of the model decreases much faster with increasing temperature than i
n real water. However, this failure, which is a common feature of the polar
izable water models, is rather unimportant in the narrow temperature range
studied here. In analyzing the molecular level structure of water as a func
tion of the thermodynamic conditions we find that the increase of the tempe
rature as well as of the pressure has a distorting effect on the tetrahedra
l hydrogen bonded network, and it causes an increase of the fraction of the
interstitial neighbors of the molecules. These changes result in a more co
mpact structure and hence in an increase of the density of the system. When
these changes are induced by the temperature, the increasing thermal motio
n of the molecules can compensate the increase of the density, and the two
opposite effects result in the appearance of the density maximum. (C) 2001
American Institute of Physics.