{ Diamond }

Make cube dimensions 2.84 A.
Place C atoms at the corners of the cube.
Place C atoms at the faces of the cube.
Place C atoms at (0.25,0.25,0.25) (0.75,0.75,0.25) 
Place C atoms at (0.75,0.25,0.75) (0.25,0.75,0.75).
Duplicate.