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The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
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Rheology based estimates of self- and collective diffusivities in viscous liquids
C Gainaru1, S Ahlmann1, L S Röwekamp1
1Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany.
The Journal of Chemical Physics
|July 9, 2021
Summary
This study estimates the self-diffusion coefficient in viscous liquids using rheological shear spectra. The generalized Almond-West approach reveals small differences compared to direct measurements, highlighting collective effects on viscous flow.
Area of Science:
- Physical Chemistry
- Materials Science
- Rheology
Background:
- Understanding molecular dynamics in supercooled liquids is crucial for materials science.
- Direct measurement of self-diffusion coefficients in viscous liquids can be challenging.
Purpose of the Study:
- To estimate the self-diffusion coefficient of viscous liquids using rheological shear spectra.
- To generalize the Almond-West approach for analyzing molecular dynamics in supercooled liquids.
Main Methods:
- Analysis of rheological shear spectra.
- Generalization of the Almond-West approach for supercooled liquids.
- Comparison of rheology-based estimates with directly measured diffusivities.
Main Results:
- Rheology-based estimates for indomethacin, ortho-terphenyl, and trinaphthylbenzene show small, systematic deviations from direct diffusivity measurements.
- The Almond-West approach was successfully generalized for molecular dynamics in supercooled liquids.
Conclusions:
- Rheological shear spectra provide a viable method for estimating self-diffusion coefficients in viscous liquids.
- Deviations are explained by mechanical Haven ratios, quantifying collective translational effects impacting viscous flow.
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