The microscopic mechanism of bulk melting of ice

TL;DR

This study uses computer simulations to reveal the microscopic defect processes that initiate homogeneous melting in ice, highlighting the key role of specific 5+7 defects in the formation of liquid nuclei.

Contribution

It provides a detailed, trajectory-based simulation analysis of the defect mechanisms leading to homogeneous melting of ice, emphasizing the importance of 5+7 defects.

Findings

5+7 defects accumulate before melting begins

Formation of liquid nucleus is preceded by defect activity

Specific defect types are crucial in melting initiation

Abstract

We study the initial stages of homogeneous melting of a hexagonal ice crystal at coexistence and at moderate superheating. Our trajectory-based computer simulation approach provides a comprehensive picture of the events that lead to melting; from the initial accumulation of 5+7 defects, via the formation of L-D and interstitial-vacancy pairs, to the formation of a liquid nucleus. Of the different types of defects that we observe to be involved in melting, a particular kind of 5+7 type defect (type 5) plays a prominent role as it often forms prior to the formation of the initial liquid nucleus and close to the site where the nucleus forms. Hence, like other solids, ice homogeneously melts via the prior accumulation of defects.