Energy polydisperse 2d Lennard-Jones fluid in presence of flow field

Abstract

The behavior of energy polydisperse $2d$ Lennard-Jones fluid (in thin-film geometry) is studied subjected to linear flow field using molecular dynamics simulations. By considering neutral and selective substrates we systematically explore the effect of flow field on particle ordering as well as response of the system. It is shown that particle density profile, spatial organization as well as local particle identity ordering in the film are affected. Furthermore, we observe flow field induced melting associated with a decrease of effective interaction parameter, $\left< \epsilon_i^{\rm eff} \right>$, which characterizes local neighborhood identity ordering. In terms of macroscopic response, the systems show both shear-thinning and shear-thickening behaviors, and shear-thinning exponent decreases with increasing temperature and eventually attains Netwonian fluid-like behavior at sufficiently high temperature. It is found that the qualitative behaviour of one component LJ-fluid and energy polydisperse fluid with neutral substrates are similar in many respects, while the one with selective substrate shows differences. In the case of energy polydisperse system, the effect of having different substrate types is significantly manifested in the density profile near the interface, $\left< \epsilon_i^{\rm eff} \right>$, and in the viscosity. We have shown that, unlike one component fluid, it is possible to tune the macroscopic response by tuning substrate-fluid interaction in energy polydisperse fluids.