The mutual diffusion constant of binary, isotopic hard-sphere mixtures: Molecular dynamics calculations using the Green–Kubo and steady-state methods

Abstract

The mutual diffusion constant of a binary mixture of equal diameter hard spheres is estimated using the method of molecular dynamics. The mixture considered is equimolar, with a species mass ratio of ten to one in a volume that is three times the close-packed volume. Two molecular dynamics methods are used: the standard Green–Kubo technique based on the evaluation of equilibrium velocity correlation functions, and a nonequilibrium method that generates a steady diffusive flow along a composition gradient by imposing special boundary conditions on two opposing faces of the cubic volume. We find that both methods yield, within about 3%, the same value of the diffusion coefficient.