Investigation of Cluster-Induced Distortion and Conductivity of Ionic Conductor CuBr

Theoretical investigation on the local distortion in the low-temperature γ-phase of superionic conductor CuBr is carried out in terms of the cluster-distortion coupling model. It is found that this cluster-induced local distortion, giving rise to the negative expansion, is quite consistent with experimental results. The specific heat and ionic conductivity involved in the 1st-order order-disorder phase transition are also studied, showing that the defects and distortions induced therefrom play quite important roles.