Cuprous halides: Old facts and new developments

Cuprous halides are characterised by (a) large amplitude Cu+ motion relativ e to immobile halide ion cage and (b) non-integral electron transfer from C u to halogen. Recent theoretical work on Cu+ ion dynamics in Cu-halides der ived from two body interatomic potentials is reviewed in the perspective of experimental diffusion and conduction of CuBr & CuI. Calorimetric data on phase transitions in CuI have been analysed. Thermal expansion in strong an harmonic systems and its intimate connection to EXAFS has been pointed out.