The Microscopic Basis of Self Diffusion — Mutual Diffusion Relationships in Binary Liquid Mixtures

Abstract

The general relation between self and mutual diffusion coefficients in binary liquid mixtures is best described in terms of velocity cross‐correlation integrals fab. In analogy to the definition of the self diffusion coefficient in terms of a time integral over the velocity autocorrelation function, the fab are given as integrals over velocity cross‐correlation functions. As the latter coefficients are measures for the coupling of the diffusive motions between pairs of particles, they may be used for probing intermolecular interactions in liquid mixtures. The approach is illustrated in application by considering diffusion in some thermodynamically ideal systems and in systems with strong positive and negative deviations from Raoult's law.

PFG-NMR and MD Simulation Study of Self-Diffusion Coefficients of Binary and Ternary Mixtures Containing Cyclohexane, Ethanol, Acetone, and Toluene

“…Self-diffusion coefficients in mixtures are closely related to the mutual diffusion coefficients, that are needed for describing mass transfer . At infinite dilution, the self-diffusion coefficient of the infinitely diluted component in a mixture is identical with the mutual diffusion coefficient.…”

“…4−8 Self-diffusion coefficients in mixtures are closely related to the mutual diffusion coefficients, that are needed for describing mass transfer. 9 At infinite dilution, the self-diffusion coefficient of the infinitely diluted component in a mixture is identical with the mutual diffusion coefficient. Simultaneously, the selfdiffusion coefficients of the other components are not connected to the mutual diffusion coefficient at this composition.…”

Prediction of Composition-Dependent Self-Diffusion Coefficients in Binary Liquid Mixtures: The Missing Link for Darken-Based Models

“…A number of works have studied the composition dependence of velocity cross-correlations CC ij . − Weingärtner observed that velocity cross-correlations CC ij show a similar composition dependence as Kirkwood–Buff coefficients G ij . However, a derivation of a relationship between velocity cross-correlations CC ij and the thermodynamic factor Γ is not straightforward and no conclusive answer was found.…”

A local composition model for the prediction of mutual diffusion coefficients in binary liquid mixtures from tracer diffusion coefficients

“…If one or more species in a liquid mixture show strong self-association, the motion of different molecules becomes strongly correlated, and this assumption breaks down. This has been formalised by the use of velocity cross-correlations (McCall and Douglass, 1967;Weingärtner, 1990). The expression for predicting mutual diffusion coefficients in such cases (i.e., mixtures in which one species is hypothesized to dimerize) was obtained by Moggridge (2012b) as:…”