Chemifriction and Superlubricity: Friends or Foes?

Area of Science:

• Materials Science
• Tribology
• Computational Physics

Background:

• Chemifriction, the friction arising from interfacial bonding, is crucial in nanoscale systems.
• Defects in two-dimensional materials like graphene can significantly alter their tribological properties.
• Understanding these mechanisms is key for designing advanced materials and interfaces.

Purpose of the Study:

• To elucidate the atomistic mechanisms of chemifriction in defected twisted graphene.
• To discover novel self-healing mechanisms that can mitigate friction.
• To develop predictive models for friction behavior in two-dimensional material interfaces.

Main Methods:

• Fully atomistic molecular dynamics simulations using machine-learning potentials.
• Analysis of stochastic bond formation and rupture events at defect sites.
• Development of a physically motivated phenomenological model for friction prediction.

Main Results:

• Identified stochastic bond formation/rupture at vacancy defects as a source of enhanced friction.
• Discovered a shear-induced atomic transfer healing mechanism that restores superlubricity.
• Observed negative differential friction coefficients under moderate normal loads.
• Revealed a transition in friction force dependence on sliding velocity.

Conclusions:

• Defects and interfacial bonding play a critical role in graphene friction.
• A novel healing mechanism offers a pathway to engineer superlubricity.
• The findings are applicable to various defected two-dimensional material interfaces.