Devitrification and melting in vapor deposited ice

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 correlate with the structural stability of the glasses and allow 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. In addition, 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.