Pressure-Induced Structural and Dielectric Changes in Liquid Water at Room Temperature

TL;DR

This study uses a deep neural network trained on density functional theory data to analyze how pressure affects the dielectric properties and structure of liquid water at room temperature, revealing nonlinear dielectric increases and structural distortions.

Contribution

It introduces a neural network approach to study pressure-dependent dielectric and structural changes in water, providing insights consistent with experimental data.

Findings

Dielectric constant increases nonlinearly with pressure.

Water's hydrogen-bond network becomes structurally distorted under pressure.

Dipolar correlations weaken as pressure increases.

Abstract

Understanding the pressure-dependent dielectric properties of water is crucial for a wide range of scientific and practical applications. In this study, we employ a deep neural network trained on density functional theory data to investigate the dielectric properties of liquid water at room temperature across a pressure range of 0.1 MPa to 1000 MPa. We observe a nonlinear increase in the static dielectric constant $\epsilon_0$ with increasing pressure, a trend that is qualitatively consistent with experimental observations. This increase in $\epsilon_0$ is primarily attributed to the increase in water density under compression, which enhances collective dipole fluctuations within the hydrogen-bonding network as well as the dielectric response. Despite the increase in $\epsilon_0$, our results reveal a decrease in the Kirkwood correlation factor $G_K$ with increasing pressure. This decrease in $G_K$ is attributed to pressure-induced structural distortions in the hydrogen-bonding network, which weaken dipolar correlations by disrupting the ideal tetrahedral arrangement of water molecules.