There is an alternative close packing called the hexagonal close packing (hcp). See: R. Williams, The Geometrical Foundation of Natural Structure, Mineola, NY: Dover, 1979 pp. 108–109. Waterman's arrangement selects spheres in ccp with centers that are at distances less than or equal to the square root of an integer when the diameter equals 1. See: S. Waterman, "Waterman Polyhedra," Symmetry: Culture and Science, 13(1–2), 2002 pp. 129–171.