Question

In the cubic close packing, the unit cell has

• A. 4 tetrahedral voids each of which is shared by four
• 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 units cell in ccp (or fcc) = 4

$\therefore$No. of tetrahedral voids = 2 × 4 = 8