SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 64: Poster: Graphene

O 64.11: Poster

Mittwoch, 29. März 2023, 18:00–20:00, P2/EG

Force-Field Development for Graphene-Graphite Water Systems — •Otto Schullian and Roland Netz — Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany

The wetting behavior of water on graphene/graphite surfaces is strongly dependent on the force fields chosen for the water-carbon interaction. Previously developed force fields were optimized to reproduce a specific contact angle for water on graphite (in the range of 85^∘ to 95^∘). However, experiments show that the contact angle for water on graphite depends strongly on the preparation of the surface; they suggest that freshly exfoliated graphite has a surprisingly hydrophilic contact angle of 60^∘±13^∘, whereas old and potentially contaminated graphite surfaces are much more hydrophobic. For graphene the variance in contact angle is even more dramatic, ranging from 10^∘ to 127^∘.

Here, we simulate contact angles for a range of water-carbon interaction strengths for one to five layers of graphene to provide the necessary parameters for a whole range of contact angles (30^∘-115^∘). In this way, one can tune the wetting behavior in simulation. From our results, we see that the graphene with no underlying support has a contact angle 2^∘-20^∘ higher than the corresponding graphite system depending on the interaction strength. In addition, we investigate the frequency-dependent friction on flat graphene and graphite as a function of the interaction strength and the number of graphene layers via the Green-Kubo relation including a hydrodynamic correction.