The Darken Relation for Multicomponent Diffusion in Liquid Mixtures of Linear Alkanes: An Investigation Using Molecular Dynamics (MD) Simulations

Molecular dynamics (MD) simulations have been performed for binary, ternary, and quaternary liquid mixtures of linear alkanes containing 1-16 carbons. Both the self-diffusivities (Di,self) and the Maxwell-Stefan (M-S) diffusivities (?ij) were determined from the MD simulations for various mixture compositions. The selfdiffusivity was determined to be a linear function of the mass fractions (omega)j of the constituent species in the mixture: Di,self = ?(omega)j...where ?is the selfdiffusivity of infinitely dilute species i in species j. The Maxwell-Stefan diffusivity of the binary i-j pair in a multicomponent mixture was determined to be predicted reasonably well by the generalization of the Darken relation: ...ij = [xi/(xi + xj)]Dj,self + [xj/(xi + xj)]Di,self, where xi is the mole fraction of species i.