Phase behavior of metastable water from computer simulation

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7302991

Poole, P H

An extensive molecular dynamics computer simulation study of a commonly-used water pair-potential, ST2, is carried out. By conducting simulations over a wide range of liquid state points, from the stable liquid to well into the supercooled and negative P regions, it is demonstrated that the stability limit of the simulated liquid can be found, and that the behavior of the system on approaching this limit is consistent with the limit being the liquid spinodal. The ST2 liquid spinodal thus found is shown not to be re-entrant. Consistent with this finding, it is shown that the properties of the liquid at negative P away from the spinodal, though thermodynamically legitimate, are not consistent with a prediction of a re-entrant spinodal. Limited tests of another commonly-used pair-potential, TIP4P, indicate that its behavior at negative P is also inconsistent with the spinodal being re-entrant. Despite the fact that there is no re-entrant spinodal in the ST2 phase diagram, the experimentally observed properties of water are quantitatively reproduced by the ST2 model. In particular, the thermodynamic anomalies of supercooled water are shown to be present in the ST2 liquid. Evidence is presented that the source of these anomalies in ST2 is a critical point representing the onset of phase coexistence between the low and high density amorphous ices. Furthermore, the isothermal transformation of either form of amorphous ice into the other is simulated using the ST2 potential, reproducing the results of experiments. These simulation results on the amorphous solids are consistent with the possibility that the amorphous ice phase transition ends in a critical point, which in turn induces the thermodynamic anomalies observed in the supercooled liquid.

• Research Organization: Boston Univ., MA (United States)
• OSTI ID: 7302991
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
664000 -- Atomic & Molecular Physics-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
AMORPHOUS STATE
COMPUTER CODES
COMPUTERIZED SIMULATION
HYDROGEN COMPOUNDS
MATHEMATICAL MODELS
MOLECULAR MODELS
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
S CODES
SIMULATION
WATER