Bestimmung mikroskopischer Eigenschaften der (2x1) Rekonstruktion von Calcit(104)
Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Zusammenfassung der Projektergebnisse
Calcite, the most stable polymorph of calcium carbonate (CaCO3), is a prevalent mineral in nature and involved in many geological and biochemical processes. The most stable surface is the (104) plane, which is naturally exposed by this mineral. This project addressed the open topic of the microscopic surface geometry following conflicting reports in literature, in particular the presence of a surface reconstruction and the assignment of the surface symmetry properties. With this project, the microscopic structure of the pristine calcite(104) surface under ultra-high vacuum conditions is clarified. As the central result, strong evidence for the expression of a (2×1) reconstruction is given and no violation of the glide-plane symmetry element was found. This understanding was achieved by combining high-resolution non-contact atomic force microscopy (NC-AFM) imaging using functionalised tips with density functional theory (DFT) calculations and NC-AFM image simulations. In particular, experiments were performed with highly-symmetric CO-terminated tips characterised by inverse imaging before and after imaging experiments on the calcite(104) surface. By this strategy, tip changes as well as asymmetric tips could be excluded. The comparison between experimental and simulated data allowed for a verification of the DFT model geometry. A four-letter S,P,Q,R nomenclature was introduced to denote the four central surface sites on the surface, following the reconstruction and symmetry properties. The row-pairing effect was only observed for asymmetric or uncharacterised tips. Last, the adsorption of CO was investigated and two different adsorption sites were identified. Therefore, the (2×1) reconstruction has a clear effect on the adsorption properties of molecules.
Projektbezogene Publikationen (Auswahl)
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Differences in Molecular Adsorption Emanating from the (2 × 1) Reconstruction of Calcite(104). The Journal of Physical Chemistry Letters, 14(7), 1983-1989.
Heggemann, Jonas; Ranawat, Yashasvi S.; Krejčí, Ondřej; Foster, Adam S. & Rahe, Philipp
