Structural evidence for the continuity of liquid and glassy water

Francis W. Starr, Marie-Claire Bellissent-Funel, and H. Eugene Stanley Center for Polymer Studies, Center for Computational Science, and Department of Physics, Boston University, Boston, MA 02215 USA Laboratoire Léon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette, Cedex, France An open question is whether the liquid and glassy phases of water are thermodynamically distinct or continuous [1]. Here we address this question using molecular dynamics simulations in comparison with neutron scattering experiments to study the effect of temperature and pressure on the local structure of liquid water. From both simulations and experiments, we find that the liquid structure at high pressure is nearly independent of temperature, and remarkably similar to the known structure of the high-density amorphous ice (HDA). Further at low pressure, the liquid structure appears to approach the experimentally-measured structure of low-density amorphous ice (LDA)as temperature decreases. These results are consistent with continuity between the liquid and glassy phases of H2O. The structure of liquid water has been well-studied at ambient 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 network that can account for a variety of the known anomalies of water [1]. More recently, the effect of pressure on both the structure and the hydrogen bond network of liquid water has been studied experimentally [2–4] and by simulations using a variety of potentials, including the ST2 potential [5–8], the MCY potential [9], the TIP4P potential [7,8,10–12], and the SPC/E potential [13,14]. Furthermore, understanding the effects of pressure may be useful in elucidating the puzzling behavior of liquid water.