Self-diffusion of nonspherical particles fundamentally conflicts with effective sphere models
Felix Roosen-Runge1,2, Peter Schurtenberger1, Anna Stradner1
1Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden.
Summary
The effective sphere model inaccurately predicts particle diffusion, overestimating slowing effects for nonspherical particles. New simulation protocols are proposed for accurate short-time self-diffusion predictions in rod-like systems.
Area of Science:
- Physics
- Physical Chemistry
- Soft Matter Science
Background:
- Modeling diffusion of nonspherical particles is crucial for understanding biological crowding, food science, and formulation.
- Current methods often simplify nonspherical particles into effective spheres, using established sphere models for approximation.
Purpose of the Study:
- To evaluate the accuracy of the effective sphere model for nonspherical particle diffusion.
- To identify the fundamental limitations of the effective sphere model.
- To propose an improved method for predicting self-diffusion of rod-like systems.
Main Methods:
- Numerical evaluation of the hydrodynamic mobility tensor.
- Simulations incorporating hydrodynamic interactions.
- Analysis of self-diffusion in solutions of ellipsoids and rod-like assemblies.
Main Results:
- The effective sphere model significantly overestimates the slowing of self-diffusion for nonspherical particles, even at low volume fractions (<0.01).
- The model exhibits inaccuracies in the linear term relevant at lower concentrations, indicating a flawed underlying assumption.
- A new protocol for predicting short-time self-diffusion of rod-like systems was developed, showing negligible system-size effects.
Conclusions:
- The effective sphere model is fundamentally inadequate for accurately representing self-diffusion of nonspherical particles.
- A simulation-based protocol offers a more reliable approach for predicting diffusion dynamics in rod-like systems.
- Accurate modeling of particle diffusion is essential for advancements in various scientific and technological fields.
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