▎ 摘　　要

By performing molecular dynamics simulations, the interfacial atomic forces of two contacting graphene flakes are calculated to quantitatively illustrate the friction evolution from commensurate to incommensurate contacts. It is found that the atomic force distributions display moire patterns. The moire patterns for the contact stress indicate the contact quality, while the patterns for the shear stress are related to the friction force. In both the commensurate and incommensurate contacts, part of the interface atoms experiences positive friction force while the other atoms negative friction force. However, the interfacial friction distributions for the incommensurate state clearly demonstrate that the positive and negative atomic friction forces distribute more symmetry than that in the commensurate state, which produces an ultra-low effective friction force.