Nano-Elastohydrodynamics: Structure, Dynamics, and Flow in Nonuniform Lubricated Junctions

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Abstract
Structure, flow, and response characteristics of molecularly thin films of hexadecane, sheared by topographically nonuniform solid gold surfaces sliding at a relative velocity of 10 meters per second, were investigated with molecular dynamics simulations. The simulations reveal three characteristics: spatial and temporal variations in the density and pressure of the lubricant in the region confined by the approaching asperities, accompanied by asperity-induced molecular layering transitions that are reflected in oscillatory patterns in the friction force; asperity deformations and microstructural transformations mediated by the lubricant; and an onset of cavitated zones in the lubricant after the asperity-asperity collision process. The simulations extend micrometer-scale elastohydrodynamic investigations into the nanometer-scale regime and provide molecular-scale insights into the fundamental mechanisms of ultrathin film lubrication phenomena under extreme conditions.