(a) What type of stoichiometric defect is shown by AgCl and why?

(b) Calculate the efficiency of packing in case of a metal crystal for simple cubic unit cell.

(a) The stoichiometric defect shown by AgCl is Frenkel defect. This is due to the large difference between the size of Ag⁺ and Cl^- ions.

(b) In a simple cubic lattice the atoms are located only on the corners of the cube. The particles touch each other along the edge.

Thus, the edge length or side of the cube ‘a’, and the radius of each particle, r are related as

a = 2r

The volume of the cubic unit cell = a³ = (2r) ³ = 8r³

Since a simple cubic unit cell contains only 1 atom

The volume of the occupied space =

∴ Packing efficiency = %

=

= = 52.36% = 52.4%