Regensburg 2025 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 23: Polymer and Molecular Dynamics, Friction and Rheology

CPP 23.5: Talk

Wednesday, March 19, 2025, 10:45–11:00, H34

Role of Trapped Water Molecules at Sliding Contacts in Lattice-Resolved Friction Investigated with Molecular Dynamics — •Miljan Dašić and Igor Stanković — Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade, Serbia

Understanding nanoscale friction within an environment which contains water, is crucial for engineering friction-based mechanisms and characterizing surfaces. From the point of view of Friction Force Microscopy (FFM) experiments, it has been understood that the lattice resolution in water environments originates from a dry contact state, in case of which all water molecules get expelled from the gap between the microscope's tip and the studied substrate.

We have developed an All-Atom Molecular Dynamics simulation setup, for revisiting this understanding by performing a detailed analysis of the impact of water molecules present in the system on the dynamic behavior of the nanotribological contact between an amorphous SiO2 probe and a monolayer MoS2 substrate.

Our analysis of stick-slip patterns shows the entrapment of water molecules at the contact interface. These trapped water molecules act as an integral part of the probe and participate in its interaction with the substrate, hence affecting the probe's dynamics and preventing long slips. Surrounding water molecules from the capillary or layer of water exhibit a replenishing effect, acting as a water reservoir during the sliding process. Such a phenomenon enables the preservation of lattice-scale resolution across a range of normal loads.

Keywords: Molecular Dynamics; Molybdenum Disulfide; Water; Friction; Stick-Slip