Theoretical study of boundary lubrication

We analyzed the dynamics of xenon atoms as lubricant between two Ni(110) slabs in relative motion. Atomic simulations are carried out by using classical molecular dynamics with realistic empirical potentials, where nickel as well as xenon atoms are relaxed. The resistance of the xenon layer against the loading force is examined and critical forces are determined to destroy the lubricant layer at different coverages. The relative motion of slabs in the lateral direction is investigated under constant normal force as a function of coverage ranging from zero to the monolayer xenon. Important lubrication properties of xenon atoms are analyzed by calculating the variation of potential energy, lateral force, and local hydrodynamic pressure. It is predicted that the corrugation of the potential energy associated with the sliding has a minimum value at submonolayer coverage. A phononic energy dissipation mechanism together with the theoretical analysis is proposed.