Question

Silver bromide (AgBr) exhibits Frenkel imperfections. The formation enthalpy is about 0.60 eV per pair. Assume that the formation entropy is zero. (a) What fraction of the Ag+ ions are in interstitial sites just below the melting point of silver bromide? (b) The Ag+ ions are extremely mobile, permitting the establishment of equi- librium even at relatively low temperatures. Assume that a one cubic cen- timeter sample of an AgBr crystal is cooled slowly enough to maintain equilibrium. At what temperature will the crystal contain just one Frenkel pair? For AgBr: Density- 6.47 g/cm3 Molecular weight - 187.8 g/mol Melting point - 700 K.

Answer 1

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