Short-Range Structural Transformations in Water at High Pressures

TL;DR

This study uses molecular dynamics simulations to analyze high-pressure structural transformations in water, validating the Amoeba potential and exploring anomalies in hydrogen-bond networks and sound propagation.

Contribution

It demonstrates the accuracy of the Amoeba potential in modeling water's structural properties and investigates pressure-induced structural anomalies and their effects on dynamics.

Findings

A structural anomaly at ~2000 atm linked to changes in local order.

Deformation of hydrogen-bond network causes the anomaly.

Numerical results align with experimental data on sound propagation.

Abstract

We report results of molecular dynamics simulations of liquid water at the temperature T=277 K for a range of high pressure. One aim of the study was to test the model Amoeba potential for description of equilibrium structural properties and dynamical processes in liquid water. The comparison our numerical results with the Amoeba and TIP5P potentials, our results of \emph{ab initio} molecular dynamics simulations and the experimental data reveals that the Amoeba potential reproduces correctly structural properties of the liquid water. Other aim of our work was related with investigation of the pressure induced structural transformations and their influence on the microscopic collective dynamics. We have found that the structural anomaly at the pressure $p_c\approx 2000$ Atm is related with the changes of the local, short-range order in liquid water within first two coordination shells. This anomaly specifies mainly by deformation of the hydrogen-bond network. We also discuss in detail the anomalous behavior of sound propagation in liquid water at high pressures and compare numerical results with the experimental data.