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Updated: May 12, 2026

The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Universal model for accurate calculation of tracer diffusion coefficients in gas, liquid and supercritical systems
Patrícia F Lito1, Ana L Magalhães, José R B Gomes
1Department of Chemistry, Associate Laboratory CICECO, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal. patricia.lito@ua.pt
Abstract:
In this work it is presented a new model for accurate calculation of binary diffusivities (D12) of solutes infinitely diluted in gas, liquid and supercritical solvents. It is based on a Lennard-Jones (LJ) model, and contains two parameters: the molecular diameter of the solvent and a diffusion activation energy. The model is universal since it is applicable to polar, weakly polar, and non-polar solutes and/or solvents, over wide ranges of temperature and density. Its validation was accomplished with the largest database ever compiled, namely 487 systems with 8293 points totally, covering polar (180 systems/2335 points) and non-polar or weakly polar (307 systems/5958 points) mixtures, for which the average errors were 2.65% and 2.97%, respectively. With regard to the physical states of the systems, the average deviations achieved were 1.56% for gaseous (73 systems/1036 points), 2.90% for supercritical (173 systems/4398 points), and 2.92% for liquid (241 systems/2859 points). Furthermore, the model exhibited excellent prediction ability. Ten expressions from the literature were adopted for comparison, but provided worse results or were not applicable to polar systems. A spreadsheet for D12 calculation is provided online for users in Supplementary Data.
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