Nanofluidic Manifestations of Structure in Liquids: A Toy Model

Interaction with a solid boundary can alter the local order in the liquid near the boundary an effect that is of special importance in geometries where these layers of altered structure occupy a significant part of the liquid. Currently, the local order is unambiguously confirmed and visualized only in two-dimensional (2D) liquids. A 2D liquid may play the role of a toy model for more complex liquids. We use molecular dynamic simulations to study instantaneous and time-averaged particle positions and velocities, quantitative characteristics of the local order, and drag forces in a 2D Lennard-Jones liquid occupying a narrow channel with moving walls. In layers of the liquid adjacent to the walls, long-time-averaged velocity significantly deviates from the predictions of conventional hydrodynamics. In the same layers, the time-averaged local order characteristics and the particle density show significant changes, with the amplitudes of these changes depending on the thermodynamic state of the liquid, the wall roughness, and commensurability with the wall.