Engineering Physics

2.6 Structure and packing fractions of simple cubic [SC] structure

The unit cell edge lengths of this structure along the crystallographic axes and interaxial angles are equal [i.e., a = b = c and α = β = γ = 90°]. Atoms are present only at the corners of this unit cell. A corner atom is shared by eight unit cells, so that the contribution of a corner atom to a unit cell is 1/8. The cube has eight corners, hence the contribution of eight corner atoms to a unit cell or the number of atoms per unit cell = . Let ‘r’ be the radius of an atom. The surfaces of the atoms touch along the cube edges. So, the distance between the centres of two neighbouring ...