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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Polymer and Molecular Dynamics, Friction and Rheology

CPP 20.3: Talk

Tuesday, March 28, 2023, 10:15–10:30, ZEU 255

Nanoscopic Friction on Monolayer MoS₂ in Presence of Water Investigated with Molecular Dynamics — •Miljan Dašić and Igor Stanković — Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

We have implemented and applied a molecular dynamics (MD) simulation setup in order to study the nanoscopic friction on monolayer MoS₂ plate in the presence of different quantities of water. Our setup mimics a standard AFM experiment, including an amorphous SiO₂ probe, a monolayer crystalline MoS₂ plate, and water molecules in-between. Presence of water molecules matches experimental conditions of air humidity. We studied two different quantities of water: (1) full water layer - SiO₂ probe is fully immersed in water and surrounded by water molecules, and (2) capillary water - water forms a capillary around the SiO₂ probe, with lateral vacuum gaps. We conducted two modes of simulations: vertical approach of SiO₂ probe towards MoS₂ plate and lateral sliding of SiO₂ probe. There are always trapped water molecules in the gap between the probe and the plate; their number drops with the increase of temperature. We have obtained well-pronounced stick-slip friction loops; we found that an increase of the applied normal load leads to the more pronounced stick-slip behaviour, as seen in AFM experiments. The amount of water present in the studied nanoscopic tribosystem has a pronounced impact on the stick-slip frictional behaviour.