I am excited to now be able to show you how the polyhedra, linkages, and nets that we saw earlier combine to make real crystal structures! Here is the AuCu₃ structure type. It has two parts: The Au atoms make up a primitive cubic lattice. The Cu atoms does something more interesting: The Cu atoms make polyhedra that link into a network: they form octahedra that link through corner-sharing into a primitive cube framework that wraps around the Au atoms.