Percolation transition of hydration water at hydrophilic surfaces

TL;DR

This study investigates the percolation transition of water molecules adsorbed on hydrophilic surfaces, revealing how temperature and surface size influence cluster formation and spanning behavior.

Contribution

It provides new insights into the quasi-2D percolation transition of hydration water at hydrophilic surfaces, including the effects of temperature, surface size, and geometry.

Findings

Percolation transition occurs at a threshold surface coverage that increases with temperature.

The percolation threshold is weakly affected by system size in the studied range.

A two-peaks structure in cluster size distribution indicates non-spanning and spanning clusters.

Abstract

An analysis of water clustering is used to study the quasi-2D percolation transition of water adsorbed at planar hydrophilic surfaces. Above the critical temperature of the layering transition (quasi-2D liquid-vapor phase transition of adsorbed molecules) a percolation transition occurs at some threshold surface coverage, which increases with increasing temperature. The location of the percolation line is consistent with the existence of a percolation transition at the critical point. The percolation threshold at a planar surface is weakly sensitive to the size of the system when its lateral dimension increases from 80 to 150 A. The size distribution of the largest water cluster shows a specific two-peaks structure in a wide range of surface coverage : the lower- and higher-size peaks represent contributions from non-spanning and spanning clusters, respectively. The ratio of the average sizes of spanning and non-spanning largest clusters is about 1.8 for all studied planes. The two-peak structure becomes more pronounced with decreasing size of the planar surface and strongly enhances at spherical surfaces.