Nanomechanics of Atomic Friction

Abstract:
　　For well-defined contacts with sizes less than hundreds of nanometers, the friction force-displacement curves are characterized by the stick-slip behavior, which are very sensitive to surface atomic structure, lattice mismatch or incommensurability, sliding velocity, surrounding temperature, to name a few. While the stick-slip behavior can be modeled by the one-degree-of-freedom Tomlinson model, it cannot explain the role of lattice structure and interface defects. Molecular simulations, on the other hand, suffer the temporal limitations and thus have difficulties in modeling the dependence on velocity and temperature. In this work, a Peierls-type model is developed which views the sliding process as the initiation and gliding passage of interface dislocations with diffused cores. The dependence of the friction behavior on the contact size is naturally due to the introduction of the dislocation core size. The spatially inhomogeneous nature of rate-limiting processes is successfully determined, from which a quantitative comparison to the thermally activated friction behavior can be made. A number of experiments in literature will be compared.