Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Focus Session: Mineral-water interfaces II
O 36.2: Talk
Tuesday, March 10, 2026, 11:00–11:15, HSZ/0403
Ab initio exploration of water clusters on CaF2 — •Isaac Azahel Ruiz Alvarado1, Wolf Gero Schmidt1, Paul Laubrock2, Jonas Heggemann2, and Philipp Rahe2 — 1Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, Paderborn, Germany — 2Institut für Physik, Universität Osnabrück, Osnabrück, Germany
The electronic and structural properties of the CaF2(111) surface-water interface are investigated from first-principles calculations. The energetic landscape for single molecular adsorption is calculated using standard DFT with London dispersion forces corrections. Single water molecules are found to preferentially adsorb on surface Ca atoms while large diffusion energy barriers are determined that restrict lateral movement of the water molecules. Additionally, the adsorption energies for the intact water molecule are compared to dissociative adsorption.
Multiple water molecules are included in the calculations to simulate the ice-like clusters observed experimentally by high-resolution AFM data acquired with CO-terminated tips. In order to understand the formation of these clusters, hexagonal rings similar to the ice Ih motif are modeled on top of the CaF2 surface slab. The ice-surface incommensurability coupled with large diffusion barriers and preferred adsorption sites is suspected to limit the formation of a closed water monolayer. Complete water overlayers and additional structures are also calculated using molecular dynamics aided by machine learning force fields trained from ab initio calculations.
Keywords: Mineral-water interface; CaF2; Water adsorption; Density functional theory; Molecular dynamics