How do interfaces alter the dynamics of supercooled water?

TL;DR

This study uses molecular dynamics simulations to explore how interfaces influence the spatially extended and persistent dynamical heterogeneity of supercooled water, revealing that interfacial properties critically affect water mobility.

Contribution

It provides new insights into the complex, spatially extended dynamical domains of interfacial supercooled water and how they depend on interface characteristics.

Findings

Interfacial water exhibits persistent dynamical domains unlike bulk water.

The dynamical response depends critically on interface nature and definition.

Interfacial modifications can tune water's dynamical behavior.

Abstract

The structure of liquid water in the proximity of an interface can deviate significantly from that of bulk water, with surface-induced structural perturbations typically converging to bulk values at about ~1 nm from the interface. While these structural changes are well established it is, in contrast, less clear how an interface perturbs the dynamics of water molecules within the liquid. Here, through an extensive set of molecular dynamics simulations of supercooled bulk and interfacial water films and nano-droplets, we observe the formation of persistent, spatially extended dynamical domains in which the average mobility varies as a function of the distance from the interface. This is in stark contrast with the dynamical heterogeneity observed in bulk water, where these domains average out spatially over time. We also find that the dynamical response of water to an interface depends critically on the nature of the interface and on the choice of interface definition. Overall these results reveal a richness in the dynamics of interfacial water that opens up the prospect of tuning the dynamical response of water through specific modifications of the interface structure or confining material.