Molecular dynamics simulations are used to examine hysteretic effects anddistinctions between equilibrium and non-equilibrium aspects of particleadsorption on the walls of nano-sized fluidfilled channels. The force on theparticle and the system's Helmholtz free energy are found to depend on theparticle's history as well as on its radial position and the wetting propertiesof the fluid, even when the particle's motion occurs on time scales much longerthan the spontaneous adsorption time. The hysteresis is associated with changesin the fluid density in the gap between the particle and the wall, and thesestructural rearrangements persist over surprisingly long times. The force andfree energy exhibit large oscillations with distance when the lattice of thestructured nanoparticle is held in register with that of the tube wall, but notif the particle is allowed to rotate freely. Adsorbed particles are trapped infree energy minima in equilibrium, but if the particle is forced along thechannel the resulting stick-slip motion alters the fluid structure and allowsthe particle to desorb.
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