Effects of Commensurability on Stick and Slip Conditions at Solid–Fluid Interface

We report the results of molecular dynamics simulations of the frictional behavior of a Lennard–Jones fluid confined between two solid crystalline walls. To study the effects of commensurability on friction, different ratios of interatomic distances in walls and fluid were considered. In particular, numerical experiments with the same fluid confined between walls with five different lattice parameters were performed. System behavior was examined by analyzing calculated time dependencies of the friction force between fluid and solid walls and distributions of the velocities of fluid particles. Friction coefficients and slip length parameters were obtained as numerical characteristics of commensurability effects. Fluid behavior near the solid interface was analyzed through visualization of the atomistic configurations and calculation of radial distribution functions. In the performed simulations, a pronounced reduction in friction was observed for highly incommensurable configurations, when the ratio between fluid and wall interatomic distances is around 1.62.