Close packing of rods on spherical surfaces

Area of Science:

• Physics
• Materials Science
• Colloid Science

Background:

• Understanding particle packing is crucial for materials design.
• Confined geometries, like spherical surfaces, present unique packing challenges.
• Spherocylinders are model systems for anisotropic particles.

Purpose of the Study:

• To investigate the optimal packing of hard spherocylinders on a spherical surface.
• To determine how aspect ratio and particle number influence packing geometry.
• To compare spherical packing with flat-plane packing for spherocylinders.

Main Methods:

• Simulated annealing simulations.
• Molecular dynamics simulations.
• Analysis of cluster structures for varying aspect ratios (L/D) and particle numbers.

Main Results:

• Discovered a rich variety of cluster structures dependent on aspect ratio and particle count.
• Observed a transition to disordered clusters for very short rods (L/D = 0.25).
• Identified a preferred baseball-like geometry for longer rods (L/D = 0.5 or 1), forming smectic-like domains.
• Found that short rods adapt more efficiently to spherical geometry than spheres or longer rods.

Conclusions:

• Optimal packing of spherocylinders on spherical surfaces is highly sensitive to particle number and aspect ratio.
• Short rods exhibit superior adaptability to spherical confinement compared to spheres and longer rods.
• Results predict behavior for experimental systems like colloidal rods at emulsion droplet interfaces.