Theory and simulation of sliding friction

When an external force acts on an adsorbate structure, the structure may slide or flow relative to the substrate. The mechanism behind this sliding motion is of fundamental importance for the understanding of friction and lubrication between two flat macroscopic surfaces. Here I present a study of the nonlinear (in the external driving force) sliding friction which is found to exhibit hysteresis giving rise to the well-known phenomenon of ‘‘stick-and-slip’’ motion. The theory predicts that for a large class of sliding systems, the ratio ${\mathit{f}}_{\mathit{k}}$/${\mathit{f}}_{\mathit{s}}$ between the kinetic and the static friction coefficients equals 1/2, in good agreement with experimental data.