MD simulations of diffusivities in methanol-n-hexane mixtures near the liquid-liquid phase splitting region

Molecular Dynamics (MD) simulations have been carried out to determine the self-diffusivities in binary mixtures of methanol and n-hexane with varying compositions at four different temperatures of 303.15 K, 307.7 K, 310.7 K, and 313.15 K. The Darken relation was used to determine both the Fick diffusivity and the Maxwell-Stefan diffusivity. The values of the Fick diffusivity obtained from the simulations are in very good agreement with published experimental data of Clark and Rowley [17]. These diffusivities approach zero near composition regions where liquid-liquid phase splitting occurs. On the other hand, the Maxwell-Stefan diffusivity is well-behaved and appears to be practically insensitive to the complex thermodynamics.