Two-phonon Raman spectra of tetragonal crystals ZnP2, CdP2, and TeO2

Two-phonon Raman spectra of ciystals ZnP2, CdP2, and Te02 were measured. All these ciystals are gyrotropic and belong to P41212 or P43212 enantiomorphous space symmetry groups. The selection rules for overtones and combined tones at high symmetry points Γ, Z, A, M, X and R of Brillouin zone were obtained using irreducible projective representations of wave vector symmetry groups Zero slope points were identified too. It was determined lines, which correspond to overtones of point Γ and vibrations on boundary Brillouin zone.