Surface reconstructions govern ice nucleation on silver iodide.

Area of Science:

• Materials Science
• Surface Science
• Crystallography

Background:

• Silver iodide (AgI) is a highly effective ice-nucleating agent.
• Its efficiency is linked to lattice matching with hexagonal ice.
• The atomic-level mechanism and surface structure of AgI's ice nucleation are not fully understood.

Purpose of the Study:

• To elucidate the atomic-level mechanism of ice nucleation by AgI.
• To determine the atomic structure of basal AgI surfaces.
• To understand how surface structure influences ice nucleation efficiency.

Main Methods:

• Noncontact atomic force microscopy (nc-AFM) in ultrahigh vacuum.
• Advanced computational modeling (e.g., density functional theory).
• Analysis of surface reconstructions on AgI basal planes.

Main Results:

• The Ag-terminated (0001) AgI surface reconstructs to a (2 × 2) structure with ordered Ag vacancies.
• This Ag-terminated surface preserves a hexagonal arrangement of atoms, facilitating epitaxial ice growth.
• The I-terminated (000[Formula: see text]) AgI surface shows a rectangular reconstruction, hindering continuous ice layer formation.

Conclusions:

• Surface atomic structure critically determines ice nucleation efficiency on AgI.
• The Ag-terminated basal plane, with its specific reconstruction, is primarily responsible for efficient ice nucleation.
• Understanding these surface structures is key to designing better ice-nucleating agents.