Topological defects and bulk melting of hexagonal ice

TL;DR

This study uses molecular dynamics and metadynamics to investigate how topological defects facilitate bulk melting in hexagonal ice, revealing defect formation and clustering as key steps in the phase transition.

Contribution

It introduces a combined simulation approach to identify the role of topological defects in ice melting, highlighting defect clustering and their long-lived nature.

Findings

Defects cluster into a region of about 50 molecules.

Defect formation triggers the transition to liquid.

Defects preserve tetrahedral coordination during melting.

Abstract

We use classical molecular dynamics combined with the recently developed metadynamics method [A. Laio and M. Parrinello, Procs. Natl. Acad. Sci. USA 99, 20 (2002)] to study the process of bulk melting in hexagonal ice. Our simulations show that bulk melting is mediated by the formation of topological defects which preserve the coordination of the tetrahedral network. Such defects cluster to form a defective region involving about 50 molecules with a surprisingly long life-time. The subsequent formation of coordination defects triggers the transition to the liquid state.