A deterministic theory describing the behavior of an ultrathin lubricant film
between two atomically-smooth solid surfaces is proposed. For the description
of lubricant state the parameter of excess volume arising due to chaotization
of solid medium structure in the course of melting is introduced. Thermodynamic
and shear melting is described consistently. Dependences of friction force on
temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon
surfaces are analyzed. Within the framework of a simple tribological model the
stick-slip mode of friction, when the lubricant periodically melts and
solidifies, is described. The obtained results are qualitatively compared with
the experimental data.Comment: 14 pages, 6 figures, 33 reference