Anomalies in the concentration fluctuations and the mutual diffusion coefficient of 2-dimensional Lennard-Jones mixture in the supercritical region

Molecular dynamics simulations on 2-dimensional Lennard-Jones mixture in the supercritical region are performed at many state points. The number of the molecule in the unit cell is 1600 and the mole fraction is 0.5. The concentration fluctuations near the critical point are large compared to the ideal mixing. The self-diffusion coefficient and the mutual diffusion coefficient are calculated. The mutual diffusion coefficient normalized by the self-diffusion coefficient has a small value near the critical point because of the large concentration fluctuation. The joint diffusion coefficients between the different species are compared to discuss the molecular motion in the supercritical region and that in the normal state. (C) 1998 Elsevier Science B.V.