Dresden 2026 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 5: Focus Session: Mineral-water interfaces I
O 5.6: Vortrag
Montag, 9. März 2026, 12:15–12:30, HSZ/0403
Atomically Resolved Imaging of the Gypsum (010) surface — •David Kugler, Andrea Conti, Tun Sinner, Florian Mittendorfer, Michael Schmid, Gareth S. Parkinson, Ulrike Diebold, and Jan Balajka — Institute of Applied Physics, TU Wien, Vienna, Austria
Gypsum (CaSO4·2H2O), the dihydrate of calcium sulfate, is the most abundant sulfate mineral in Earth′s crust and it is widely used as a fertilizer and as a construction material. Its bulk crystal structure consists of alternating calcium sulfate bilayers and bilayers of crystal water. While the water in the bulk has been extensively studied, a comprehensive understanding of surface processes is still missing. Water is, however, present on all surfaces in ambient environment and influences surface chemistry. Because the adjacent layers are linked only by hydrogen bonds, gypsum cleaves readily along the (010) plane, exposing large, atomically flat terraces. In this work, noncontact atomic force microscopy (nc-AFM) with a qPlus sensor was used to resolve the atomic structure of the cleaved gypsum (010) surface and to visualize the configuration of adsorbed water. Our results indicate that one of the surface crystal water molecules rotates into a lower energy orientation, forming a hydrogen bond with the second crystal water molecule within the unit cell. Preliminary ab-initio modeling suggests that the first adsorbed water layer preserves the periodicity of the bulk structure by forming hydrogen bonds with the surface crystal water.
Keywords: gypsum; surface; water; afm; qPlus