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Kinetic Frustration Effects on Dense Two-Dimensional Packings of Convex Particles and Their Structural
Charles Emmett Maher1, Frank H Stillinger1, Salvatore Torquato1,2,3,4
1Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
The Journal of Physical Chemistry. B
|March 2, 2021
Summary
Kinetic effects influence how particles pack, causing deviations from densest arrangements. Varying compression rates impacts packing fraction and order, especially for less symmetric particles.
Area of Science:
- Physics
- Materials Science
- Discrete Geometry
Background:
- Hard-particle packing is crucial across multiple scientific disciplines.
- Most research focuses on densest packings, often neglecting kinetic influences.
- Real-world packing involves dynamic processes affecting final configurations.
Purpose of the Study:
- To investigate how kinetic effects, specifically compression/shear rates, alter hard-particle packing structures.
- To quantify the deviation from densest possible configurations due to kinetic factors.
- To understand the impact of kinetics on particle ordering and packing fraction.
Main Methods:
- Utilized a stochastic adaptive shrinking cell (ASC) optimization scheme.
- Varied the number of particle moves between compression/shear steps to simulate different time scales.
- Generated 2D packings of various noncircular particle shapes (triangles, rhombi, lenses, etc.).
- Introduced the kinetic frustration index (K) to measure deviations from maximum packing fraction.
- Analyzed spectral densities and contact networks to assess ordering.
Main Results:
- Kinetic effects significantly alter packing fraction and order.
- The degree of kinetic influence depends on particle shape, specifically asphericity, curvature, and rotational symmetry.
- Found that particles with higher asphericity, less curvature, and less rotational symmetry exhibit more pronounced kinetic effects.
- Developed a quantitative measure, the kinetic frustration index (K), to characterize these effects.
Conclusions:
- Kinetic factors are critical in determining the final state of hard-particle packings.
- Particle shape plays a key role in the sensitivity of packing to kinetic influences.
- Findings are relevant for optimizing laboratory packing protocols and understanding natural granular systems.
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