THE TEMPERATURE-DEPENDENT STRUCTURE OF POINT-DEFECT COMPLEXES IN SILVER-CHLORIDE CRYSTALS

Evidence of a temperature-induced, cyclable transition in the structur e of point-defect complexes in AgCl crystals is reported. The effect i s attributed to an entropy-driven change in the equilibrium structure of defect configurations, analogous to a phase transition in bulk soli ds. Such a transition is likely to occur in a system where the entropy term is a significant part of the defect Gibbs free energy, and where the energies of different defect configurations are very close. A cru de thermodynamic analysis provides an estimate of the energy and entro py changes associated with the transition.