A comparison study between the Lennard-Jones and DRIP potentials for friction of graphene layers

Graphene is a promising solid lubricant, in particular for small-length scale devices such as nano/micro-electro-mechanical systems. Atomistic simulations such as molecular dynamics is a popular tool to study the frictional behaviors of graphene layers and it is of critical importance to accurately describe the interlayer interactions in order to give a reliable prediction on the friction of graphene. In this study, the interlayer interactions between graphene layers are examined by using two interatomic potentials, Lennard-Jones (LJ) potential and dihedral-angle-corrected registry-dependent interlayer (DRIP) potential, in the molecular dynamics simulations of friction sliding of multilayer graphene structures. While both potentials have the identical attractive interactions, DRIP models the repulsive interaction by registry-dependent modifiers considering transverse distance and dihedral angle. The sliding simulations mimic the atomic force microscope experiment and are carried out in the zigzag (ZZ) and armchair (AC) directions. The simulation results reveal that the friction forces of the DRIP models are about one order of magnitude larger than those of the LJ models in both sliding directions. It turns out that the modification of the repulsive term in DRIP introduces additional energy corrugations which increase the friction force. Moreover, it is found that the sliding direction is another important factor on friction force of graphene layers so that in both LJ and DRIP models the friction force in the AC sliding direction is about two to three times larger than that of the ZZ sliding.