Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions

TL;DR

This study uses first-principles molecular dynamics with nonlocal van der Waals interactions to better simulate liquid water, revealing more compact structures and improved agreement with experimental properties at near ambient conditions.

Contribution

It introduces a computationally efficient scheme incorporating nonlocal van der Waals interactions into first-principles simulations of water, enhancing structural accuracy.

Findings

More compact liquid water structures with van der Waals interactions

Diminished role of hydrogen-bond directionality in structure

Improved agreement with experimental properties

Abstract

We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed analysis comprising the study of the partial radial distribution functions, various local order indices, the hydrogen-bond network, and the selfdiffusion coefficient. The explicit treatment of the van der Waals interactions leads to an overall improved description of liquid water.