sentences:  α-Aluminium has a regular cubic close packed structure, fcc, where each aluminium atom has 12 nearest neighbors, 6 in the same plane and 3 above and below and the coordination polyhedron is a cuboctahedron.α-Iron has a body centered cubic structure where each iron atom has 8 nearest neighbors situated at the corners of a cube.The two most common allotropes of carbon have different coordination numbers.