  This letter deals with triply-periodic (crystalline) solutions in a family of
Skyrme systems, namely where the field takes values in the squashed 3-sphere.
The family includes the standard Skyrme model (round 3-sphere), and the
Skyrme-Faddeev case (maximal squashing). In the round case, the lowest-energy
crystal is the well-known cubic lattice of half-skyrmions; but in the squashed
case the minimal-energy crystal structures turn out to be different. We
describe some of the solutions that arise, including arrays of vortices and
multi-sheeted structures.
