Assessment of elastic models in supercooled water: A molecular dynamics study with the TIP4P/2005f force field

TL;DR

This study evaluates elastic models' effectiveness in predicting the dynamics of supercooled water using molecular dynamics simulations with the TIP4P/2005f force field, revealing good agreement and identifying regimes related to viscosity and relaxation times.

Contribution

It provides the first comprehensive assessment of elastic models for supercooled water's shear viscosity and relaxation times using molecular dynamics simulations.

Findings

Elastic models accurately describe supercooled water dynamics.

Two regimes of viscosity are identified with a crossover near the Stokes-Einstein violation point.

Shear properties are key to understanding flow activation energy.

Abstract

Glass formers exhibit a viscoelastic behavior: at the laboratory timescale, they behave like (glassy) solids at low temperatures, and like liquids at high temperatures. Based on this observation, elastic models relate the long time supercooled dynamics to short time elastic properties of the supercooled liquid. In the present work, we assess the validity of elastic models for the shear viscosity and the $\alpha$-relaxation time of supercooled water, using molecular dynamics simulations with the TIP4P/2005f force field over a wide range of temperatures. We show that elastic models provide a good description of supercooled water dynamics. For the viscosity, two different regimes are observed and the crossover temperature is found to be close to the one where the Stokes-Einstein relation starts to be violated. Our simulations show that only shear properties are important to characterize the effective flow activation energy. This study calls for experimental determination of the high frequency elastic properties of water at low temperatures.