Question

In the cubic close packing, the unit cell has

• A. $4$ tetrahedral voids each of which is shared by four adjacent unit cells
• B. $4$ tetrahedral voids within the unit cell
• C. $8$ tetrahedral voids each of which is shared by four adjacent unit cells
• D. $8$ tetrahedral voids within the unit cells

Answer 1

Answer: (D)

$8$ tetrahedral voids within the unit cells

Answer 2

Cubic close packing is also called face centred cubic. No. of atoms per unit cell in $ccp$ (or $fcc) = 4$ $\therefore$ No. of tetrahedral voids $= 2 \times 4 = 8$