Atomic-scale insights into frictional energy dissipation mechanisms

Lukas Hörmann, Shinjae Nam, Alfred J. Weymouth, Franz J. Gießibl, and Reinhard J. Maurer

Friction causes significant energy loss in any moving mechanical device. As the miniaturisation of devices reaches the quantum limit, so do dynamical dissipation processes. Fundamentally quantum mechanical mechanisms govern friction at the atomic-scale. We account for all relevant quantum mechanical effects, such as charge transfer, or van der Waals interactions, by em­ploying density functional theory, and machine learning and use the probe particle model to simulate energy dissipation.

Using this approach, we investigate dynamic friction at the natural limit of a singular atom moving a single chemical bond. This enables us to explore how the local bonding environment of the underlying sample surface affects the energy dissipation that a probe particle experiences. Focussing on the example of a CO-functionalised lateral force microscope that measures frictional energy dissipation above various organic adlayers on Cu(111), we find strong correlations between the local bonding environment and the energy dissipation. Our findings capture the qualitative trends found in experiment.

Finally, we present a mechan­istic inter­preta­tion of our findings that provides insights into the underlying physics of atomic/lateral force micro­scopy measurements.

Figure 1. Schematic of a lateral force microscopy measurement of fric­tional energy dissipation; CO-functionalised tip probes dif­fer­ent local bonding environments.