Topological properties of interfacial hydrogen bond networks

Hydrogen bonds play a crucial role in the anomalous behavior of water. While the properties of individual H-bonds have been extensively studied, the topological characteristics of the resulting H-bond network remain less explored. In this study, we employ molecular dynamics simulations to examine various aqueous interfaces, uncovering an increased number of H-bonds parallel to surfaces compared to bulk water. To quantify the topology of these networks, we introduce novel estimators for network percolation and dimensionality. Our findings reveal that the elevated proportion of H-bonds parallel to the interface significantly influences network connectivity, reducing both the number of water layers and the distance from the surface at which the network achieves full connectivity. Consequently, H-bond networks at interfaces exhibit more "two-dimensional" characteristics than those in bulk water due to high local water density and the competition between water-water H-bonds and water-surface interactions.