Schottky defect

        Frenkel defect

(i)        It occurs when the

equal number of vacant

cation and anion sites are

found in lattice structure.        

(i) It occurs when ions

(usually cations) are

missing from the correct

lattice sites and occupy

the interstitial positions.

(ii) Due to this defect, the

density of the crystal is

decreased.

(ii) It does not effect the

density of the crystal.

(iii) It is present in highly

ionic compounds having

nearly similar size of

cation and anion with

high coordination number

Example : NaCl, CsCl

etc.

(iii)    It is found in the

compounds of low

coordination number and

the size of the cation is

smaller than anion.

Examples : ZnS, AgCl

etc.