Concentration and mass dependence of transport coefficients and correlation functions in binary mixtures with high mass-asymmetry

TL;DR

This study investigates how transport properties and correlation functions in a binary Lennard-Jones mixture depend on particle mass asymmetry, revealing a generalized Stokes-Einstein relation and cage effects at high mass ratios.

Contribution

It demonstrates the concentration and mass dependence of transport coefficients in high mass-asymmetry binary mixtures, including the limiting case of infinite mass ratio.

Findings

Product of heavy species diffusion coefficient and mixture shear viscosity remains constant across parameters.

Large mass ratios induce cage effects observable in multiple correlation functions.

Generalized Stokes-Einstein relation holds over a wide range of compositions and mass ratios.

Abstract

Correlation functions and transport coefficients of self-diffusion and shear viscosity of a binary Lennard-Jones mixture with components differing only in their particle mass are studied up to high values of the mass ratio $\mu$, including the limiting case $\mu=\infty$, for different mole fractions $x$. Within a large range of $x$ and $\mu$ the product of the diffusion coefficient of the heavy species $D_{2}$ and the total shear viscosity of the mixture $\eta_{m}$ is found to remain constant, obeying a generalized Stokes-Einstein relation. At high liquid density, large mass ratios lead to a pronounced cage effect that is observable in the mean square displacement, the velocity autocorrelation function and the van Hove correlation function.