Efficiency of H center stabilization in alkali halide crystals at low-temperature uniaxial deformation

The efficiency of stabilization of H centers as well as its dependence on the degree of uniaxial deformation are considered within the framework of the modified geometric model of alkali halides. It is shown that stabilization of H centers is difficult in KI and RbI crystals, while in other NaCl-type crystals it becomes quite probable. Under uniaxial deformation, the interstitial space, in which the defect will be located, decreases, and the efficiency decrease. In the case of cesium halides, the orientation of the H centers takes place predominantly in the direction; therefore, the criteria for their stabilization differ from the NaCl-type alkali halide crystals. According to calculations, in CsI, large displacements of the nearest neighbors are required to stabilize H centers; while in CsBr their stabilization becomes sensitive to the effect of uniaxial deformation. The efficiency of H center stabilization obtained by the geometric model is compared with the corresponding efficiencies obtained from the theory of local excitations and the calculated total probability of accumulation of H centers under the influence of uniaxial deformation.