Name the structural units of the silicon crystal lattice.

The crystal structure of silicon is classified according to the structure of diamond [139] and therefore has two atoms in a primitive cell. The silicon crystal lattice can be represented in the form of two penetrating face-centered cubic lattices with a cube side a = 0.543 nm. The structure is visualized as a tetrahedron with four vertices of the first lattice at (0,0,0), (a / 2,0,0), (0, a / 2,0) and (0,0, a / 2) and an additional atom added to the center of this tetrahedron. The additional atom is displaced relative to the original lattice.