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Molecularly thin liquid films of alkanes in extreme conditions in a boundary lubrication regime have been investigated. The wall is modeled as a rough atomic sinusoidal wall. The effect on the boundary condition of the roughness characteristics, given by the period and amplitude of the sinusoidal wall, is studied here. The effect of the molecular length of the lubricating fluid is also examined here. The results show that the relative size of the fluid molecules and wall roughness determines the slip or nonslip boundary conditions. The effect of wall roughness characteristics on the rheological properties of the lubrication film is also studied.

A molecular dynamics simulation of a thin liquid film as it is sheared between two planar walls is reported. The model liquid is composed of linear chain molecules of hexadecane (C16H34) with intramolecular architecture such as bond stretching, angle bending and dihedral potentials included in the model. Designing a model that can mimic the planar shear flow enables us to study important questions on the effects of the wall properties on the slip between the liquid film and the wall. Different properties of the wall such as wall density, wall stiffness and wall–fluid interaction strength have been studied to determine the slip between the wall and fluid. The slip has been investigated for strong and weak adsorbing surfaces at various shear rates. The results emphasize the importance of adsorption on the degree of slip. The dependence of slip on the film thickness is also demonstrated.