Water nanodroplets freezing and ice crystal formation on subcooled surfaces

The freezing behavior of liquid water, resulting in solid phases such as glassy structures, hexagonal crystals, or cubic crystals, is influenced by surface supercooling. This study identifies three distinct freezing modes of water nanodroplets on platinum surfaces through molecular dynamics simulations. At surface temperatures below 175 K, water nanodroplets freeze into a solid phase characterized by a glassy structure. Between 176 and 195 K, nucleation begins within the amorphous solid, resulting in crystalline ice formations. In the temperature range of 196-209 K, nucleation and growth occur within the liquid nanodroplets, culminating in the formation of ice crystals exhibiting cubic and hexagonal morphologies. Interestingly, the water temperature rises by 20-37 K during ice crystal nucleation and growth, and the proportion of cubic ice relative to hexagonal ice decreases as the temperature rises. Additionally, a specific threshold involving molecular distance and kinetic energy is essential for the formation of regular ice crystals, thereby confining heterogeneous nucleation to a defined range of surface temperatures. This study offers valuable insights that could inform strategies for controlling ice crystallization in various applications.