Slip in nanoscale shear flow: Mechanisms of interfacial friction

The atomistic mechanism of fluid-solid interfacial friction as the basis of slip is still not fully understood. This study explores the interfacial friction mechanisms and their interplay with the nanoscale slip behavior using non-equilibrium molecular dynamics simulations. Our results show that there is an abrupt jump of slip length at a critical shear rate, corresponding to the transition from "defect slip" at low shear rates to "collective slip" at high shear rates. Here, we identified two mechanisms of interfacial friction: surface potential and collision mechanisms. Their impacts on slip are elaborated through a quantitative scaling estimation and our results show that both mechanisms contribute to the defect slip at low shear rates, while the collision mechanism dominates the collective slip at high shear rates. We also verify the importance of the bulk viscous heating via a comparison among different thermostat strategies.