  Colloidal crystal structures with complexity and diversity rivaling atomic
and molecular crystals have been predicted and obtained for hard particles by
entropy maximization. However, so far homochiral colloidal crystals, which are
candidates for photonic metamaterials, are absent. Using Monte Carlo
simulations we show that chiral polyhedra exhibiting weak directional entropic
forces self-assemble either an achiral crystal or a chiral crystal with limited
control over the crystal handedness. Building blocks with stronger faceting
exhibit higher selectivity and assemble a chiral crystal with handedness
uniquely determined by the particle chirality. Tuning the strength of
directional entropic forces by means of particle rounding or the use of
depletants allows for reconfiguration between achiral and homochiral crystals.
We rationalize our findings by quantifying the chirality strength of each
particle, both from particle geometry and potential of mean force and torque
diagrams.
