If $$\mathrm{AgI}$$ crystallises in zinc blende structure with $$\mathrm{I}^{-}$$ ions at lattice points then the fraction of tetrahedral voids occupied by $$\mathrm{Ag}^{+}$$ ions is

Which of the following defect lowers the density of a solid?

When a cation leaves its normal position in the crystal and moves to some interstitial space, the defect in the crystal is known as