Effect of Charge Transfer on Phonon Dynamics of Polarizable Materials

This Paper gives the connection between the polarization of ions and the repulsive force between them. We have investigated the phonon dynamics of Polarizable Materials in NaCl phase using Rigid Shell Model with pair wise interionic interaction potential. The potential consist of the long -range Coulomb and three-body interactions and the short -range van der Waals interaction and the Hafemeister and Flygare type overlap repulsion extended up to the second neighbor ions. The present model basically includes the effect of charge transfer caused by the electron-shell deformation of the overlapping ions in the frame work of both ions polarizable. this takes account of the polarizability of ions for vibrations of all wavelengths. There is generally good agreement between the measured dispersion relations and the dispersion relations calculated on the simple version of the shell model-Coulomb forces between ions of unit charge with the iodine atoms polarizable and central repulsive forces between first neighbors only, acting through the iodine shell. The elastic constants obtained from the model have been used to calculate the phonon dispersion relation in the symmetry direction .