Equilibrium, thermal defect reactions

The light-induced and thermal equilibrium defect reactions are aspects of the same general process. Indeed, the structural models proposed are virtually identical (compare Figs. 6.13 and 6.30). In the two-well description of Fig. 6.1, excitation over the barrier in either direction can, in principle, be thermal or by an external excitation. The... 

Anti-Frenkel disorder similar to Frenkel disorder except that the interstitials are anions and vacancies are therefore in the anion sublattice. In Zr02 the reaction is 0 kS + 0[ and the anti-Frenkel equilibrium constant is K p = [ko ][On- This type of thermal defect is found in lattices that have a fluorite structure (CaF2, Zr02), which means that there are many large interstitial sites where the anions can be accommodated, but not the cations because their charge is larger, and they are less well screened from each other. 

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