Transport properties of 2D Lennard–Jones fluid: effect of particle size polydispersity

Abstract

ABSTRACT We performed molecular dynamics simulation to investigate the transport coefficients of 2D size polydisperse Lennard–Jones fluids considering two size distributions, namely, Gaussian (G) and Uniform (U). In particular, we investigate how transport coefficients like viscosity (η), self-diffusion (D) and thermal conductivity (κ) are affected by particle size polydispersity (δ). For both systems, it is found that η is a non-monotonic function of δ, i.e. η gradually decreases and then increases as one vary δ across terminal polydispersity δ t . The re-entrant freezing at large δ due to increase fractionation may describe this behaviour. Dynamics of different size particles indicate that small particles tend to be more diffusive and contribute significantly to the collective diffusion according to SE relation. The self-diffusion coefficient obtained from the collective dynamics of the particles and the fluid's viscosity agree well with one another. It is noted that the thermal conductivity, κ, exhibits a decreasing trend with both δ and T as a result of the decreasing correlation in particle arrangement and the increase in defect such as vacancies or interstitials in the structure or composition due to polydispersity. Finally, it is shown that the particle size polydispersity of the developed material may be tuned to obtain the desired κ value.