Probing defects and correlations in the hydrogen-bond network of ab initio water

TL;DR

This paper investigates the correlation patterns of defects in the hydrogen-bond network of ab initio water, revealing their similarities to solid phases and robustness across different potential approximations.

Contribution

It provides a detailed analysis of defect correlations in water's hydrogen-bond network and compares them to solid phases, highlighting their directional nature and robustness.

Findings

Defects are highly correlated and resemble solid phase structures.

Coordination defect correlations involve weaker yet directional hydrogen bonds.

Structural features of the hydrogen bond network are robust across potential models.

Abstract

The hydrogen-bond network of water is characterized by the presence of coordination defects relative to the ideal tetrahedral network of ice, whose fluctuations determine the static and time-dependent properties of the liquid. Because of topological constraints, such defects do not come alone, but are highly correlated coming in a plethora of different pairs. Here we discuss in detail such correlations in the case of ab initio water models and show that they have interesting similarities to regular and defective solid phases of water. Although defect correlations involve deviations from idealized tetrahedrality, they can still be regarded as weaker hydrogen bonds that retain a high degree of directionality. We also investigate how the structure and population of coordination defects is affected by approximations to the inter-atomic potential, finding that in most cases, the qualitative features of the hydrogen bond network are remarkably robust.