Alpha-iron cube. Computer graphic of a cubic model of a crystal of alpha-iron. Iron (Fe) atoms are depicted as spheres. This structure is known as a body- centred cubic cystal" in that atoms occur at each corner of the cube, with one in the centre, linked by atomic bonds. Iron is a silver-white metal capable of taking a high polish, ductile, malleable, and can be welded when hot. Three allo- tropic forms of iron are known, with alpha-iron forming at temperatures cooler than 769 degrees Celsius. At this temperature, Fe atoms bond into the shape seen, Iforming an extensive lattice. This shape has also been used in architectural design, as used in the"