Frenkel defects arises when an ion occupies an interstitial position between the lattice points. This defect occurs generally in ionic crystals in which the anion is much larger in size than the cation. AgBr is an example for this type of defect.
One of the Ag+ ion occupies a position in the interstitial space rather than its own appropriate site in the lattice is shown in Figure.
Fig: Frenkel Defects in a Crystal
The crystal remains neutral since the number of positive ions is the same as the number of negative ions.