Calculation of second-order Raman scattering for KBr, NaCl, and MgO crystals

The polarized second-order Raman spectra of KBr, NaCl, and MgO are calculated, using a simple model based on the Born and Bradburn approach. The breathing-shell model is used to calculate phonon energies and phonon polarization vectors, and consequently the polarizability tensor. The model takes into account interionic anharmonic forces and involves only two free parameters, of which one determines the shape of the various spectra for a given crystal, and the other gives the intensity ratio between two of these spectra. The main features of the experimental spectra are reproduced. An analysis of the spectra is given, which takes into account the phonon-eigenvector composition as well as the phonon energies.