抄録
Raman scattering measurements were performed in the benitoite-type BaTiSi_3O_9, BaZrSi_3O_9, BaSnSi_3O_9 and tetragermanatetype BaGe_4O_9 phases in order to elucidate the spectroscopic and structural features of D_<2/v>G (T_3O_9)-type compounds (expressed by Smith's notation) with the GO_6 octahedral unit isolated by the T_3O_9 ring. The Raman band assignments in middle and high wavenumber region wes also carried out. In addition, the wavenumber of antisymmetric stretching vibration mode, ν_<as>, for Si-O-G bond was calculated by means of combination of the simple molecular model and Badger's rule, and compared with the experimental results. It was suggested that the v_<as> was governed by the force constant of T-O_<ax> bond, which was connected with the G^<4+>.
