Single-crystal I ice surfaces unveil connection between macroscopic and molecular structure

Area of Science:

• Surface science
• Crystallography
• Materials science

Background:

• The physics and chemistry of ice surfaces are crucial for biological and environmental processes.
• Connecting macroscopic ice crystal faces to their molecular structure is essential for scientific understanding.
• The microscopic structure of ice Ih crystals, composed of stacked molecular hexagons, is known but its link to macroscopic shapes is unclear.

Purpose of the Study:

• To experimentally link the macroscopic shape of ice crystals to their microscopic hexagonal structure.
• To provide direct evidence connecting surface etch pit patterns to crystallographic orientations.
• To explain the observed switch in the most stable ice face between the ice-water and ice-vapor interfaces.

Main Methods:

• Fabrication of large ice single crystals with specific faces (basal, primary prism, secondary prism) exposed.
• Capturing macroscopic etch pit images of the ice surfaces.
• Acquiring electron backscatter diffraction (EBSD) orientation density function (ODF) plots for the same samples.

Main Results:

• Direct comparison of etch pit images and EBSD ODF plots compellingly links macroscopic hexagonal profiles to microscopic crystallographic hexagons.
• Experimental data confirms the relationship between macroscopic surface features and the underlying molecular structure of ice.
• A model based on prism face molecular structure explains the change in surface stability between different interfaces.

Conclusions:

• The study successfully connects macroscopic ice crystal morphology to its fundamental molecular structure.
• The findings provide a direct experimental bridge between observable ice shapes and crystallographic details.
• Understanding these connections is vital for various scientific disciplines impacted by ice surface phenomena.