Room temperature compressibility and diffusivity of liquid water from first principles

TL;DR

This study uses first-principles molecular dynamics to compute water's compressibility and diffusivity at room temperature, comparing two van der Waals functionals and analyzing their accuracy against experimental data.

Contribution

It provides a detailed ab initio analysis of water's compressibility and diffusivity, highlighting the importance of functional choice in simulations of liquid water.

Findings

Both functionals predict compressibility within ~30% of experimental values.

Only one functional accurately reproduces the density dependence of self-diffusion.

Discrepancies are explained by differences in liquid structure at various densities.

Abstract

The isothermal compressibility of water is essential to understand its anomalous properties. We compute it by ab initio molecular dynamics simulations of 200 molecules at five densities, using two different van der Waals density functionals. While both functionals predict compressibilities within ~30% of experiment, only one of them accurately reproduces, within the uncertainty of the simulation, the density dependence of the self-diffusion coefficient in the anomalous region. The discrepancies between the two functionals are explained in terms of the low- and high-density structures of the liquid.