Theory of atomic level sliding friction between ideal crystal interfaces

Recent theoretical work on atomic level sliding friction is summarized. Some previous analytic results are verified by numerical simulations, and finite-size scaling arguments based on several time scales appropriate to finite crystals undergoing shear motion are used to interpret the results of the simulations and to give insight into the methods by which energy is dissipated in such a shearing process. One conclusion is that the existence of a lifetime for the lattice vibrations plays an important role in determining the velocity dependence of the force of friction, for any finite-size crystal. Finally the force of friction found in recent microbalance experiments between a solid rare-gas-element film on a metallic substrate is calculated by the present methods and compared to experiment. The main conclusion is that the observed friction is probably due to atomic level defects such as substitutional impurities. Larger-scale defects on the surface contribute a much smaller value.