Chemistry · Ch 6 — Solid State
Frenkel Defect
Frenkel Defect
Frenkel defect arises when an ion is dislodged from its normal lattice position and instead relocates to occupy an interstitial position elsewhere in the structure -- rather than leaving the crystal altogether, as happens in a Schottky defect. This defect is seen in ionic solids where the cation and anion differ noticeably in size, since it is specifically the smaller of the two ions that is able to squeeze into the interstitial gaps between the regular lattice sites. AgBr is the standard example: the comparatively small Ag+ ion leaves its normal lattice site and takes up an interstitial position instead, while the larger Br- ions stay put. …
What this figure shows. A grid of teal '-' spheres (Br-) and red '+' spheres (Ag+) forming an ionic lattice, with two lattice sites labelled 'Ag+ Missing' where a red sphere is absent, and arrows pointing from those gaps to nearby off-lattice positions labelled 'Ag+ in interstitial position', where the displaced Ag+ ions have relocated between the regular lattice sites; a legend keys red-plus to Ag+ and teal-minus to Br-, …