Adjacent sheets of the f.c.c. structure are then assumed to collapse on each other, leading to the observed simple-cubic packing. Simple cubic might in fact be the closest — and thus ...

Platinum-nickel alloy excavated nano-multipods with hexagonal close-packed structure and superior activity towards hydrogen evolution reaction. Nat. Commun. 8, 15131 doi: 10.1038/ncomms15131 (2017).