  The premelting of ice is well known, but little is known about how the
premelted and solid surfaces convert to each other. In this work, the
transition dynamics between two phases are revealed with large-scale molecular
dynamics simulations. Supercooling and superheating states exist in the
transition, and are overcome by nucleation-like processes. The natural
inhomogeneity of ice surfaces enhances nuclei formation, while it only
accelerates premelting but not freezing. Furthermore, the complete freezing of
ice surfaces may be hindered by the stacking order mismatch between nuclei.
This work points out the importance of metastable states in premelting, and the
necessity of a large system scale in describing its transition process.

Chemical Physics;Materials Science