  The assembly of colloids in nematic liquid crystals via topological defects
has been extensively studied for spherical particles, and investigations of
other colloid shapes have revealed a wide array of new assembly behaviors. We
show, using Landau-de Gennes numerical modeling, that nematic defect
configurations and colloidal assembly can be strongly influenced by fine
details of colloid shape, in particular the presence of sharp edges. For
cylinder, microbullet, and cube colloid geometries, we obtain the particles'
equilibrium alignment directions and effective pair interaction potentials as a
function of simple shape parameters. We find that defects pin at sharp edges,
and that the colloid consequently orients at an oblique angle relative to the
far-field nematic director that depends on the colloid's shape. This
shape-dependent alignment, which we confirm in experimental measurements,
raises the possibility of selecting self-assembly outcomes for colloids in
liquid crystals by tuning particle geometry.

Soft Condensed Matter