Energy polydisperse fluid under cylindrical confinement

The thermodynamic melting/freezing transition (T∗) behavior and particle dynamics under cylindrical confinement of a model energy polydisperse (EP) fluid are investigated by means of molecular dynamics simulations. All the particles in the system are different whose identity is characterized by the interaction energy parameter εi drawn randomly from a uniform distribution, and thus, the system represents an extreme limit of a multi-component system. It is observed that confinement induces shift in T∗ for both the EP and reference one-component (1C) fluid systems from their respective bulk values, and the direction of the shift is sensitive to the density. Although the trend of shift is similar for both the systems, the value of T∗ for the EP system is consistently above the 1C system for the considered different degrees of confinement. Neighborhood identity ordering (NIO) driven by the preferential interaction among the particles is observed in EP systems which is more pronounced near/below T∗. Unlike in bulk, confinement driven morphology of NIO in the form of alternate rings of higher/lower εi particles is observed. The particles with εi values near and below the mean show hopping motion between these annular regions. We believe that the observed complex dynamics in confined EP fluid could be utilized in practical applications where the mid εi particles can be used as carriers between the core and the curve surface of the narrow confinement for efficient and even distribution of substance of interest which needs to be adsorbed on the surface of a long narrow channel.