Which of the following statements for crystals having Frenkel defect is not correct?
Frenkel defects are observed where the difference in sizes of cations and anions is large
The density of crystals having Frenkel defect is lesser than that of a pure perfect crystal
In an ionic crystal having Frenkel defect may also contain Schottky defect
Usually alkali halides do not have Frenkel defect
ln frenkal defect ions is shifted in its interstitial site but density remains unchange