A phenomenological approach was considered for clarifying such defects in ionic crystals. Quantitative agreement was obtained by using a simple cube-root law for the defect-defect interaction potential. This approach was applied to AgCl, AgBr, AgI, PbF2, with rock salt, fluorite and wurtzite structures, various types of disorder (Frenkel, anti-Frenkel) and various types of phase transition (solid-liquid, solid-solid, first-order, second-order). The predicted defect-defect interaction led to a quantitative description of conduction anomalies and to the expectation of a phase instability at a temperature which was very close to the actual transition.

N.Hainovsky, J.Maier: Radiation Effects and Defects in Solids, 1995, 137[1-4], 267-71