Show that in a cubic close packed $(ccp)$ structure,eight tetrahedral voids are present per unit cell.

(N/A) In a $ccp$ structure,the unit cell is divided into $8$ small cubes.
Each small cube has atoms at alternate corners [Fig. $(a)$].
In total,each small cube has $4$ atoms.
When these $4$ atoms are joined to one another,they form a regular tetrahedron.
Thus,there is one tetrahedral void in each small cube,resulting in $8$ tetrahedral voids in total per unit cell.
Since each of the eight small cubes contains one void,the total number of tetrahedral voids is $8$.
We know that a $ccp$ structure has $4$ atoms per unit cell. Thus,the number of tetrahedral voids is twice the number of atoms $(2 \times 4 = 8)$.