Mass dependence of the self diffusion coefficients in two equimolar binary liquid Lennard-Jones systems determined through molecular dynamics simulation

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Abstract
Careful molecular dynamics simulations have been made on the mass dependence of the self diffusion coefficients of two liquid Lennard-Jones systems corresponding, respectively, to equimolar solutions of ‘argon(1)-argon(2)’ and ‘argon(1)-krypton(2)’. In each case the mass m 1 of component 1 was held at 39·948 amu, and the mass m 2 of component 2 was varied over a wide range, holding constant the potential parameters, mole fractions, density and temperature. The linear contributions to the slopes of the curves in a log-log plot of the diffusion coefficients versus m 2/m 1 were found to be of the order of -0·25. This was justified heuristically and, in the ‘argon-argon’ case, on the basis of a perturbation theory developed by Ebbsjö and collaborators. The analogous linear contributions for the diffusion coefficient ratios D 1/D 2 in a log-log plot versus m 2/m 1, were found to be much weaker, 0·064 and 0·075, respectively.