Microscopic insights into the onset of slip in Lennard-Jones fluids

The phenomenon of hydrodynamic slip of simple fluids at a fluid-solid interface is well-described by Molecular-Kinetic Theory (MKT), which relates slip velocity to the fluid shear rate and various thermodynamic and fluid-specific parameters. In this work, we perform extensive molecular-dynamics (MD) simulations of slip in fluids consisting of Lennard-Jones chains of varying lengths, with the goal of elucidating the role played by a kinetic length scale that is present within the MKT formalism. By performing non-linear model fits to our MD data, we demonstrate that MKT is a strong candidate to describe slip in Lennard-Jones chains. In particular, we show that the onset of slip varies as a function of chain length and molecular weight, which we rationalize in terms of the MKT framework. We close by briefly comparing our results with experimental studies of hydrodynamic slip in polymeric liquids.