Cooperative Origin of Low-Density Domains in Liquid Water

TL;DR

This study uses Monte Carlo simulations and geometric analysis to show that low-density regions in liquid water form through cooperative clustering of tetrahedral molecules, mainly as linear, non-compact structures.

Contribution

It demonstrates the cooperative formation of low-density, ice-like regions in liquid water using a combination of simulation and Voronoi tessellation analysis.

Findings

Low-density regions form via cluster accretion exceeding a minimum size.

Clusters are predominantly linear and become less compact as they grow.

Further accretion beyond a certain size does not decrease density.

Abstract

We study the size of clusters formed by water molecules possessing large enough tetrahedrality with respect to their nearest neighbors. Using Monte Carlo simulation of the SPC/E model of water, together with a geometric analysis based on Voronoi tessellation, we find that regions of lower density than the bulk are formed by accretion of molecules into clusters exceeding a minimum size. Clusters are predominantly linear objects and become less compact as they grow until they reach a size beyond which further accretion is not accompanied by a density decrease. The results suggest that the formation of "ice-like" regions in liquid water is cooperative.