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08. April 2025, 16:00 until 16:05

Johanna Hütner, TU Wien, IAP, FB Oberflächenphysik

Seminar

Silver iodide – surface structure and ice nucleation investigated by noncontact AFM

Silver iodide (AgI) is used as an efficient cloud seeding agent due to its good lattice match with hexagonal ice. However, the basal AgI surfaces are polar and thus inherently unstable. The mechanism for polarity compensation requires surface modifications, which may disrupt the epitaxial relationship with hexagonal ice. Atomically resolved noncontact atomic force microscopy (NC-AFM) images reveal that AgI basal planes undergo surface reconstuctions to compensate polarity. The Ag-terminated surface forms a (2 × 2) reconstruction with hexagonal symmetry, whereas the I-terminated surface adopts a complex reconstruction with rectangular symmetry. Upon exposure to water vapor at 100 K in UHV, ice growth occurs in different modes on the two terminations. An epitaxial ice layer forms only on the Ag-terminated surface, whereas the reconstruction of the I-terminated surface prevents epitaxial ice growth. Computational modeling of AgI is challenging, with results strongly dependent on the choice of functional. Random phase approximation (RPA) calculations were used to obtain a stable model matching the experiment.

These atomic-level observations could enhance our understanding of heterogeneous ice nucleation in the atmosphere.

Calendar entry

Event location: SEM.R. DB gelb 05 B
1040 Wien
Wiedner Hauptstraße 8-10/E134
Organiser: IAP
Manuela Marik
marik@iap.tuwien.ac.at
Public: Yes
Entrance fee: No
Registration required: No

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Past Events

Johanna Hütner, TU Wien, IAP, FB Oberflächenphysik

Event details