Structural and dynamic anomalous properties of TIP4P/2005 water at extreme pressures

TL;DR

This study uses molecular dynamics simulations to explore the anomalous structural and dynamic properties of TIP4P/2005 water under extreme pressures, confirming experimental findings and linking anomalies to hydrogen bond network reorganization.

Contribution

It provides detailed simulation data on water's behavior at high pressures, revealing the connection between structural reorganization and dynamic anomalies.

Findings

Confirmed the existence of a minimum in structural relaxation time under pressure.

Linked the anomalies to sudden hydrogen bond network reorganization.

Achieved good agreement with experimental viscosity measurements.

Abstract

Water shows numerous thermodynamic, dynamic, and structural anomalies. Recent experiments [Eichler et al. Phys. Rev. Lett. 134, 134101 (2025)], based on measurements of shear and bulk viscosities of liquid water up to 1.6 GPa, have reported the existence of a minimum in the variation of the structural relaxation time {\tau}{\alpha} with pressure at room temperature. Here we investigate this and related properties with molecular dynamics simulations of the TIP4P/2005 water model, performed at extreme pressures commensurate with the experiments. Specifically, we compute dynamic (self-diffusion, shear and bulk viscosities, and structural relaxation time) and structural (oxygen-oxygen radial distribution function and structure factor, translational order parameter) properties down to 220 K and up to 2.7 GPa. We find good agreement with the experimental observations, and confirm the existence of a minimum in {\tau}{\alpha} . The microscopic information obtained from the simulations suggests that this anomaly is connected with the sudden reorganization of the hydrogen bond network induced by pressurization.