Chemistry - Solid State Question with Solution | TestHub

In an fcc unit cell, the effective number of atoms is $Z=4$.

The number of tetrahedral voids in a close-packed structure is twice the number of effective atoms.

Number of tetrahedral voids = $2Z=2\times 4=8$.

Alternatively, in an fcc unit cell, tetrahedral voids are located on the body diagonals. There are $4$ body diagonals and each contains $2$ tetrahedral voids.

Total number of tetrahedral voids = $4\times 2=8$.

Answer: $8$