Molecular dynamics simulations of the friction experienced by graphene flakes in rotational motion

Atomic scale friction of graphene strongly depends on the commensurability which is related to the rotational motion. Despite the crucial role of the rotational motion of bi-layer graphene, there is no direct study of it. In this paper, the mechanism of the rotational motion of the graphene flake on graphene substrate using molecular dynamics simulations was studied. Simulation model with rotational force was developed to observe the friction behavior of graphene. Various parametric studies were performed by controlling variables such as flake size, load, orientation of rotational force and spring constant. Graphene flakes with commensurate orientations showed a clear stick-and-slip motion during the rotation. Variation of flake size and load affected adhesion force which caused the nonlinear friction behavior. Two specific stacking orientations, namely AA and AB stacking, showed relatively stable rotational motion compared to others. Translational motion was also observed simultaneously during slip event of AA and AB stacking orientation. Finally, based on these overall observations, the pathway of flake by rotation was explained along with the effect of spring constant.