Friction contribution to water-bond breakage kinetics

TL;DR

This study uses molecular dynamics simulations and Fokker-Planck analysis to quantify how local friction influences water molecule bond breakage kinetics, revealing significantly increased friction in tightly coordinated water.

Contribution

It introduces a method to separate free-energy and friction effects in water bond breakage dynamics using mean first-passage times and diffusivity profiles.

Findings

Friction in tightly coordinated water is six times higher than in bulk water.

Friction effects dominate the separation kinetics in certain water configurations.

The dominant reaction path involves additional orthogonal coordinates.

Abstract

Based on the trajectories of the separation between water molecule pairs from MD simulations, we investigate the bond breakage dynamics in bulk water. From the spectrum of mean first-passage times, the Fokker-Planck equation allows us to derive the diffusivity profile along the separation coordinate and thus to unambiguously disentangle the effects of free-energy and local friction on the separation kinetics. For tightly coordinated water the friction is six times higher than in bulk, which can be interpreted in terms of a dominant reaction path that involves additional orthogonal coordinates.