Moiré pattern based universal rules governing interfacial superlubricity: A case of graphene

Abstract

With the development of advanced manufacturing, superlubricity, with a friction coefficient smaller than 0.001, is highly expected at the contacting surfaces. It has been revealed that the Moiré pattern formed between two crystalline surfaces could take a crucial effect on structural superlubricity. Whereas how to tune tribological properties by manipulating the Moiré patterns is still not well studied and understood. In this work, a misfit interval statistical method (MISM) is developed to identify the geometrical characteristics of a Moiré pattern quantitatively, in which the distribution of lattice misfits can act as a good indicator to demonstrate (non-)superlubricity at the interfaces. Both the contact size (D) and the twist angle (θ) substantially affect the distribution of misfits and hence play a dominant role in affecting frictional properties. Furthermore, a parameter-free model is suggested to distinguish the regimes between non-superlubricity and superlubricity in the D-θ diagram. For the case of twisting bilayer graphene, the prediction made by this model are in good agreement with molecular dynamics (MD) simulation results. The model is generic to the other homogenous and heterogeneous interfaces, and the results in this work provide a new perspective on tuning interfacial superlubricity based on the Moiré patterns.