Molecular dynamics simulation of boundary slip in nanogap: effect of shear velocity

Molecular dynamics (MD) simulations using the polymer consistent force field (PCFF) were adopted to investigate the density, molecular and velocity distributions of lubricant squalane in nanogap at 293 K, three different film thicknesses and a wide range of shear velocities. The lubrication mechanism and boundary slip were analyzed. The results showed that the lubricant atoms tended to form layers parallel to the confining wall. The distances between the layers of lubricant atoms were irregular rather than broadening far away from the walls and were about three to four times the length of C C bond in the squalane. The tendency of lubricant atoms to form layers and the density of solid-like layer increased with decreasing film thickness. It was clearly to find the boundary slip at the solid-liquid interface from the velocity profile. The slip lengths increased with increasing velocity of substrates at the beginning, and then decreased. When the film thickness was 3.44 nm, the maximum slip length was 4.35 nm at the substrate velocity of 22.8 m·s-1. According to the simulations, the relationship between the slip length and the shear velocity was given. © All Right Reserved.