Devitrification and Melting Dynamics in Vapor Deposited Water Ice

TL;DR

This study uses simulations to analyze how vapor deposited and quenched amorphous ices melt and devitrify, revealing surface-initiated melting in vapor deposited ice and structural stability indicators.

Contribution

It introduces a new algorithm to analyze hydrogen-bond networks, linking ring statistics to structural stability and nucleation behavior in amorphous ices.

Findings

Vapor deposited ice melts starting at the surface, unlike bulk melting in quenched ice.

Vapor deposited ice shows more 5-membered rings near the surface, promoting crystallization.

The Avrami exponent exceeds standard values in vapor deposited ice, indicating higher kinetic stability.

Abstract

The equilibration dynamics of ultrastable glasses subjected to heating protocols has attracted recent experimental and theoretical interest. With simulations of the mW water model, we investigate the devitrification and melting dynamics of both conventional quenched (QG) and vapor deposited (DG) amorphous ices under controlled heating ramps. By developing an algorithm to reconstruct hydrogen-bond networks, we show that bond ring statistics correlates with the structural stability of the glasses and allows tracking crystalline and liquid clusters during devitrification and melting. We find that QG melts in the bulk, whereas melting in DG preferentially begins near the free surface. During devitrification, the DG shows an excess of 5-membered rings near the free surface, which is consistent with its tendency to nucleate the crystal phase in this region. Additionally, the DG shows an Avrami exponent exceeding the standard 1+d behavior, while both glasses display the same sub-3d growth of liquid clusters across heating rates, indicating that the DG enhanced exponent stems from its higher kinetic stability.