Infrared spectroscopy investigation of the CsHSeO4 superionic phase transition

The temperature dependence of the polarized infrared reflectivity spectra o f cesium hydrogen selenate is reported between room temperature and 170 deg rees C, and analyzed in the framework of the four-parameter model of the di electric function. The results of the simulation show that the hydrogen-bon d breaking starts far below Te and the ratio eta of protons involved in H-b ond chains follows the law eta(T)=exp[E/(T-T-0)] with E=5,3 K and T-0=129 d egrees C. The protonic superionic phase transition is shown to occur at a t opological threshold from a one-dimensional structure of Il bonding to a st ructure of liquidlike nature. Such a microscopic mechanism, i.e., H-bond br eaking, is consistent with previous results and explains the peculiar behav ior of the elastic properties.