Two-phonon Raman spectra of tetragonal crystals ZnP_2, CdP_2, and TeO_2

摘要

Two-phonon Raman spectra of crystals ZnP_2, CdP_2, and TeO_2 were measured. All these crystals are gyrotropic and belong to P4_12_12 or P4_32_12 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.