APPLICATION OF THE METHOD OF PROJECTIVE REPRESENTATIONS TO THE ANALYSIS OF SECOND-ORDER RAMAN SCATTERING SPECTRA IN ENANTIOMORPHOUS TETRAGONAL CRYSTALS

We propose a method to determine the selection rules for two-phonon transitions and zero-slope points in the Brillouin zone with the use of irreducible projective representations. The appropriate calculations are carried out for points A, Z; A; M; X, and R of the first Brillouin zone of tetragonal enantiomorphous crystals that are described by the space symmetry groups P 4(1)2(1)2 and P4(3)2(1)2. The results of these calculations are applied to the analysis of the spectra of two-phonon Raman scattering (RS) in the crystals of zinc and cadmium diphosphides, alpha-ZnP2 and CdP2, and paratellurite TeO2.