The Battle of Grand Gulf was fought on April 29, 1863, during th: A lower symmetry version of the truncated tetrahedron (a truncated tetragonal disphenoid with order 8 D2d symmetry) is called a Friauf polyhedron in crystals such as complex metallic alloys. This form fits 5 Friauf polyhedra around an axis, giving a 72-degree dihedral angle on a subset of 6-6 edges.[citation needed] It is named after J. B. Friauf and his 1927 paper "The crystal structure of the intermetallic compound MgCu2".[4]