Introduction:
AgBr is a compound that exhibits both Frankel and Schottky defects. These defects occur due to the presence of vacant lattice sites or the movement of ions within the crystal lattice. In the case of AgBr, both types of defects are observed, leading to the deviation from perfect crystalline structure.

Frankel Defect:
A Frankel defect occurs when an ion or atom leaves its original lattice site and occupies an interstitial position within the crystal lattice. In the case of AgBr, silver ions (Ag+) can move from their original positions and occupy interstitial sites between the bromide (Br-) ions. This creates a vacancy at the original lattice site, resulting in a Frankel defect.

Schottky Defect:
A Schottky defect occurs when pairs of cations and anions are missing from their lattice sites, creating vacancies in the crystal lattice. In AgBr, both silver (Ag+) and bromide (Br-) ions can form Schottky defects. Some silver ions may be missing from their lattice sites, leaving behind vacant positions. Similarly, some bromide ions may also be missing, creating additional vacancies.

Presence of both Defects in AgBr:
AgBr exhibits both Frankel and Schottky defects due to the relative sizes of silver and bromide ions. The silver ions are larger in size compared to the bromide ions. This size difference allows the silver ions to occupy interstitial positions without significantly distorting the crystal lattice. At the same time, the smaller bromide ions can form vacancies in the lattice due to their relative mobility.

Summary:
In summary, AgBr shows both Frankel and Schottky defects. The presence of Frankel defects occurs when silver ions move to interstitial positions, creating vacancies at their original lattice sites. On the other hand, Schottky defects arise from the absence of both silver and bromide ions, leading to vacancies in the crystal lattice. The relative sizes of silver and bromide ions allow for the occurrence of both types of defects in AgBr.