Question

In cubic close packing, the unit cell has:

(a) 4 tetrahedral voids each of which is shared by 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

(d) 8 tetrahedral voids within the unit cells.

ccp = hcp

No. of atoms per unit cell in fcc unit cell = 4.

∴ No. of tetrahedral voids = 2 × 4 = 8