Structure of supercooled and glassy water under pressure
Francis W. Starr,
1
Marie-Claire Bellissent-Funel,
2
and H. Eugene Stanley
1
1
Center for Polymer Studies, Center for Computational Science, and Department of Physics, Boston University,
Boston, Massachusetts 02215
2
Laboratoire Le ´on Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France
Received 25 January 1999
We use molecular-dynamics simulations to study the effect of temperature and pressure on the local struc-
ture of liquid water in parallel with neutron-scattering experiments. We find, in agreement with experimental
results, that the simulated liquid structure at high pressure is nearly independent of temperature, and remark-
ably similar to the known structure of the high-density amorphous ice. Further, at low pressure, the liquid
structure appears to approach the experimentally measured structure of low-density amorphous ice as tempera-
ture decreases. These results are consistent with the postulated continuity between the liquid and glassy phases
of H
2
O. S1063-651X9910007-2
PACS numbers: 64.70.Pf, 61.12.Ex, 61.20.Ja, 61.43.Fs
The structure of liquid water has been well-studied at am-
bient pressure by a variety of experimental and simulation
techniques. It has been recognized that each water molecule
is typically hydrogen bonded to four neighboring molecules
in a tetrahedral arrangement, leading to an open bond net-
work that can account for a variety of the known anomalies
of water 1,2. More recently, the effect of pressure on both
the structure and the hydrogen bond network of liquid water
has been studied experimentally 3,4 and by simulations us-
ing a variety of potentials, including the ST2 potential 5,6,
the MCY potential 7, the TIP4P potential 6,8–10, and the
SPC/E potential 11. Furthermore, understanding the effects
of pressure may be useful in elucidating the puzzling behav-
ior of liquid water 12,13.
In particular, three competing ‘‘scenarios’’ have been hy-
pothesized to explain the anomalous properties of water: i
the existence of a spinodal bounding the stability of the liq-
uid in the superheated, stretched, and supercooled states
14; ii the existence of a liquid-liquid transition line be-
tween two liquid phases differing in density 6,10,15–17;
iii a singularity-free scenario in which the anomalies are
related to the presence of low-density and low-entropy struc-
tural heterogeneities 18.
Here, we present molecular-dynamics MD simulations
Table I of a comparatively large system of 8000 molecules
23,24 interacting via the extended simple point charge
SPC/E pair potential 25. We find remarkable agreement
with neutron-scattering studies of the effect of pressure on
the structure of liquid D
2
O 4, indicating that the SPC/E
potential reproduces many structural changes in the liquid
FIG. 1. Pair correlation function h ( r ) for two of five temperatures studied Table I. The curves can be identified as follows reading from
top to bottom at the location of the arrow: P =600 MPa,465 MPa,260 MPa,100 MPa,0.1 MPa, and -200 MPa. Pressures are the same for
the experiments and simulations, with the exception that no experiment was possible at P =-200 MPa. Note the pronounced increase in the
3.3 Å peak arrow when pressure is increased. To facilitate comparison with experiments, the simulation temperature is reported relative to
the T
MD
of the SPC/E potential at atmospheric pressure. Similarly, the experimental data are reported relative to the T
MD
of D
2
O at
atmospheric pressure. The behavior of the simulated h ( r ) strongly resembles the experimental results. b The pair correlation function
g
OO
( r ) for three of five temperatures studied Table I. Note the pronounced increase in the 3.3 Å peak arrow when pressure is increased.
The curves may be identified as in a. c The molecular structure factor S
M
( q ) , calculated from the Fourier transform of h ( r ) a. Looking
at the first peak in S
M
( q ), the curves are identified as described in a. Note the shift in the first peak when pressure is increased.
PHYSICAL REVIEW E JULY 1999 VOLUME 60, NUMBER 1
PRE 60 1063-651X/99/601/10844/$15.00 1084 ©1999 The American Physical Society