Unravelling the surface structure and reactivity of the calcite (1014) cleavage plane by threedimensional force field spectroscopy

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Calcite is the most stable polymorph of calcium carbonate and abundant in the geological environment. Consequently, the surface structure and reactivity of calcite surfaces are of utmost importance for various fields, including biomineralization and scale inhibition. Many of these areas have in common that they are governed by the interaction of certain molecules with the calcite surface.The most stable cleavage plane of calcite, calcite (1014), is known to exhibit distinct deviations from the bulk-truncated structure. While the existence of these deviations is free of doubt, the physical origin remains unresolved so far.In this project, we aim at unravelling the surface structure and reactivity by measuring the three-dimensional force field of the (1014) calcite cleavage plane using high-resolution atomic force microscopy in ultra-high vacuum. Force field spectroscopy allows for mapping the three-dimensional force field acting between the tip of the microscope and the sample surface down to the atomic level. Special emphasis will be on understanding temperaturedependent changes of the surfaces properties in the temperature range from low (30 K) to elevated temperatures (370 K).To investigate the surface reactivity of the calcite cleavage plane with respect to understanding the interaction of amino acids with this surface, we will functionalize the microscope tip with a COOH-moiety. Upon performing three-dimensional force spectroscopy with such a tip, we will gain site-specific information on attraction and repulsion as well as the interaction range felt by the COOH group, mimicking the interaction of amino acids with the calcite cleavage plane.