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

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 ε₀ with increasing pressure, a trend that is qualitatively consistent with experimental observations. This increase in ε₀ is primarily attributed to the increase in water density under compression, which enhances collective dipole fluctuation on the hydrogen-bond network as well as the dielectric response. Interestingly, despite the increase in ε₀, our results reveal a decrease in the Kirkwood correlation factor G_K. This decrease 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. These findings provide important insights into the behavior of liquid water under pressure, with broader implications for fields ranging from materials science to environmental studies.