Edge premelting of two-dimensional ices.

Area of Science:

• Surface Science
• Condensed Matter Physics
• Materials Science

Background:

• Bulk ice surfaces exhibit a quasi-liquid layer (QLL) below the melting point due to surface premelting.
• Understanding premelting phenomena is crucial for various applications, including atmospheric science and materials engineering.

Purpose of the Study:

• To investigate the phenomenon of premelting at the edges of two-dimensional (2D) bilayer hexagonal ice.
• To characterize the structure and dynamics of the resulting quasi-liquid bands (QLBs) and compare them to the bulk QLL.

Main Methods:

• Extensive molecular dynamics simulations were employed to model 2D bilayer hexagonal ice adsorbed on solid surfaces.
• Analysis focused on the premelting behavior at different edge types (armchair and zigzag) and temperatures.

Main Results:

• The edges of 2D bilayer hexagonal ice undergo premelting, forming quasi-liquid bands (QLBs).
• QLBs exhibit indistinguishable structure and dynamics from the bilayer liquid phase, serving as a lower-dimensional analog to the bulk QLL.
• QLB width at armchair edges is similar to zigzag edges at low temperatures but significantly larger near the melting point.

Conclusions:

• Edge premelting in 2D ices is a significant phenomenon, creating quasi-liquid bands.
• The temperature and chirality-dependent width of QLBs contribute to the heterogeneity of premelting.
• This finding adds a new dimension to the understanding of ice surface phenomena and phase transitions.