  For the contact of two finite portions of interacting rigid crystalline
surfaces, we compute the dependence of the pinning energy barrier on the misfit
angle and contact area. The resulting data are used to investigate the
distribution of static frictional thresholds for a contact of polycrystal
surfaces, as occurs at the touching points of dry or even lubricated friction.
The simplicity of the model allows us to investigate a broad contact-size and
angular range, thus obtaining the statistical properties of the energy barriers
opposing sliding for a single asperity. These statistical properties are used
as the input of a master-equation model to predict the sliding properties of
two macroscopic surfaces in contact. The model is consistent with the
well-established result that low temperature should generally favor stick-slip
motion, while at high temperature sliding should be smooth.
