Understanding the effects of intercalated molecules on structural superlubric contacts

Y Cheng and M Ma, PHYSICAL REVIEW MATERIALS, 4, 113606 (2020).

DOI: 10.1103/PhysRevMaterials.4.113606

Third bodies are ubiquitous in mesoand nanoscopic friction pairs. So far, few researchers have investigated their effects on structural superlubric contact which is a promising approach in reducing friction and wear. In this work, using molecular dynamics simulations we find that intercalated molecules, a typical type of third body, have multiple effects in graphite contacts. While for commensurate contacts the friction decreases with the coverage of intercalated molecules in general, for an incommensurate interface a complex dependence is observed. With state-of-the-art detailed analysis, we reveal that with coverage increases, for commensurate contacts the change in contact area accounts for the variation in friction. For incommensurate contacts, the resistance due to the direct interaction between intercalated molecules and the slider dominates the energy dissipation. For both kinds of contacts, complex transitions in the structures and kinetic behaviors of intercalated molecules are observed. Our results provide an overall picture for the effects of intercalated molecules on friction in structural superlubric systems.

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