  We study the optimal packing of short, hard spherocylinders confined to lie
tangential to a spherical surface, using simulated annealing and molecular
dynamics simulations. For clusters of up to twelve particles, we map out the
changes in the geometry of the closest-packed configuration as a function of
the aspect ratio $L/D$, where $L$ is the cylinder length and $D$ the diameter
of the rods. We find a rich variety of cluster structures. For larger clusters,
we find that the best-packed configurations up to around 100 particles are
highly dependent on the exact number of particles and aspect ratio. For even
larger clusters, we find largely disordered clusters for very short rods ($L/D
= 0.25$), while slightly longer rods ($L/D = 0.5$ or $1$) prefer a global
baseball-like geometry of smectic-like domains, similar to the behavior of
large-scale nematic shells. Our results provide predictions for experimentally
realizable systems of colloidal rods trapped at the interface of emulsion
droplets.
