Packing efficiency of metal crystal in simple cubic lattice :
Step 1 : Radius of sphere : In simple cubic unit cell, particles (spheres) are at the corners and touch each other along the edge.

A face of simple cubic unit cell is shown in Fig. It is evident that
a = 2r or r = a/2 ………(1)
where r is the radius of atom and ‘a’ is the length of unit cell edge.
Step 2 : Volume of sphere : Volume of a sphere = .
Substitution for r from Eq. (1)
∴ Volume of one particle = =
Step 3 : Total volume of particles : Because simple cubic unit cell contains only one particle, volume occupied by particle in unit cell =
Step 4 : Packing efficiency
Packing efficiency =
=
= 52.36%
Thus, in simple cubic lattice, 52.36 % of total space is occupied by particles and 100−52.36 = 47.64 % is empty space,
∴ void volume or a percentage of void space=.47.64 %