Molecular dynamics simulations were performed for binary, ternary, and quaternary liquid mixtures of linear alkanes containing 1 to 16 carbons. Both the self-diffusivities (Di,seif) and the Maxwell-Stefan diffusivities (Dij) were determined from the molecular dynamics simulations for various mixture compositions. The self-diffusivity was determined to be a linear function of the mass fractions ωj of the constituent species in the mixture: Di,self = Σj=1j=nωjDi,selfxj→1 where Di,selfxj→1 was the self-diffusivity of infinitely dilute species i in species j. The Maxwell-Stefan diffusivity of the binary i-j pair in a multi-component mixture was determined to be predicted reasonably well by the generalization of the Darken relation: Dij = [xi/(xi + x j)]Dj,self + [xj/(xi + x j)]Di,self, where xi was the mole fraction of species i.

The Darken Relation for Multi-Component Diffusion in Liquid Mixtures of Linear Alkanes: an Investigation using Molecular Dynamics (MD) Simulations. Krishna, R., Van Baten, J.M.: Industrial and Engineering Chemistry Research, 2005, 44[17], 6939-47