Mw. Mahoney et Wl. Jorgensen, A five-site model for liquid water and the reproduction of the density anomaly by rigid, nonpolarizable potential functions, J CHEM PHYS, 112(20), 2000, pp. 8910-8922
The ability of simple potential functions to reproduce accurately the densi
ty of liquid water from -37 to 100 degrees C at 1 to 10 000 atm has been fu
rther explored. The result is the five-site TIP5P model, which yields signi
ficantly improved results; the average error in the density over the 100 de
grees temperature range from -37.5 to 62.5 degrees C at 1 atm is only 0.006
g cm(-3). Classical Monte Carlo statistical mechanics calculations have be
en performed to optimize the parameters, especially the position of the neg
ative charges along the lone-pair directions. Initial calculations with 216
molecules in the NPT ensemble at 1 atm focused on finding a model that rep
roduced the shape of the liquid density curve as a function of temperature.
Calculations performed for 512 molecules with the final TIP5P model demons
trate that the density maximum near 4 degrees C at 1 atm is reproduced, whi
le high-quality structural and thermodynamic results are maintained. Attain
ment of high precision for the low-temperature runs required sampling for m
ore than 1 billion Monte Carlo configurations. In addition, the dielectric
constant was computed from the response to an applied electric field; the r
esult is 81.5 +/- 1.5 at 25 degrees C and the experimental curve is mirrore
d from 0-100 degrees C at 1 atm. The TIP5P model is also found to perform w
ell as a function of pressure; the density of liquid water at 25 degrees C
is reproduced with an average error of similar to 2% over the range from 1
to 10 000 atm, and the shift of the temperature of maximum density to lower
temperature with increasing pressure is also obtained. (C) 2000 American I
nstitute of Physics. [S0021-9606(00)50820-4].