Rod packings and crystal chemistry

Some crystallographic packings of identical infinite cylinders are described. It is shown how certain crystal structures are related to these packings when the cylinders are replaced by rods of atoms or groups of atoms (coordination polyhedra). Emphasis is placed on the densest cubic rod packing and structures based on this principle, which include garnet, Th₃P₄, β-Mn, Ag₄RbI₅ and bixbyite.