Distinct Diffusion Coefficients in Binary Nonelectrolyte Mixtures: Frames of Reference

Abstract

Generalized transport coefficients are indispensable for the study of interactions between species of the same kind in binary solutions. Distinct diffusion coefficients are best suited for this purpose because of their finite limiting values and inherent symmetry. Equations are derived for the calculation of these coefficients from experimental data for the mass-, volume-, number-, and solvent-fixed frames of reference. Distinct diffusion coefficients in the 4 reference frames computed for 14 binary nonelectrolyte solutions show that the numberfixed frame is probably best suited for the comparison of the macroscopic properties of these solutions. A point of contention has been the frame of reference of the Friedman-Mills equation;' surprisingly, the mass-fixed frame describes its Dt values closely.

Diffusive transport properties in monovalent and divalent metal-ion halide melts:A computer simulation study

“…This independence is a useful property which may be easily deduced from Eq. ͑3͒ by taking into account that both ⌳ 12 (t) and ⌳ 12 0 (t) are independent of R. The independence of R of ⌳ 12 d (t) was also observed by Mills et al 11 by manipulating the experimental distinct diffusion coefficients in different liquid mixtures.…”

“…Velocity correlation functions play a fundamental role in statistical mechanics and both self-and distinctdiffusion coefficients may be obtained from experiment. 11,12 Self-properties provide information on the motions of single atoms whereas distinct properties supply a measure of the coupling between the velocities of different particles. Distinct diffusion coefficients have been proposed to probe the ion-ion interaction models in electrolyte solutions.…”

“…10 Experimental distinct diffusion coefficients for 14 binary nonelectrolyte mixtures at different concentrations have been reported recently. 11 One of the reasons for the increasing interest on the distinct properties in multicomponent liquids may be that, unlike other transport properties, they can be related to the interactions between pairs of particles of both the same and different species. 10,11 An important complication for the interpretation of distinct properties lies in the fact that, in principle, they are defined ͑or measured͒ with respect to some specific reference frame R and their values are markedly dependent on the choice of R. 12,13 The mass-fixed ͑also called barycentric͒ and the number-fixed reference frames are commonly used in theoretical treatments.…”

“…Almost all diffusion measurements are carried out in the volumefixed frame. 11,12 We performed a preliminary MD study of the distinct properties in molten salts.…”

Distinct Diffusion in Macromolecule‐Solvent Mixtures

“…It was studied for many binary systems of electrolytes [5] and nonelectrolytes. [4,6] In a previous study we developed a new reference state of velocity correlation coefficient (VCC), based on hard sphere hydrodynamics, useful to the velocity cross-correlation analysis of real systems. [7] In the present work we use the DDC defined in Equation (1), a closelyrelated quantity, which was introduced and discussed by Summary: The specificity of interactions between pairs of molecules cannot be explicitly given by experimental transport coefficients such as intra-or mutual diffusion coefficients.…”