  We simulate a strongly size-disperse hard-sphere fluid confined between two
parallel, hard walls. We find that confinement induces crystallization into
n-layered hexagonal lattices and a novel honeycomb-shaped structure,
facilitated by fractionation. The onset of freezing prevents the formation of a
stable glass phase and occurs at much smaller packing fraction than in bulk.
Varying the wall separation triggers solid-to-solid transitions and a
systematic change of the size-distribution of crystalline particles, which we
rationalize using a semi-quantitative theory. We show that the crystallization
can be exploited in a wedge geometry to demix particles of different sizes.
