Show that in a cubic packed structure, eight tetrahedral voids are present per unit cell.

The cubic close-packed structure contains one atom at each corner of a unit cell and at the face centre of each unit cell. Each unit cell consists of 8 small cubes.

Each small cube contains 4 atoms at its alternate corner when these atoms are joined to each other lead to the creation of a tetrahedral void as shown below

since there are total 8 smaller cubes present at one unit cell and each smaller cube has one tetrahedral void hence, the total number of tetrahedral void present in each unit cell is equal to eight

As we know ccp structure has 4 atoms per unit cell. Thus, the total number of a tetrahedral void in one ccp unit cell is equal to 8.