A RAMAN-STUDY OF NEW PHOSPHO-SILICIDES - RHSI3P3 AND IRSI3P3

Raman spectra of single crystals of new phospho-silicides RhSi3P3 and IrSi3P3 confirm that the compounds crystallize in the monoclinic syste m, space group C2, which unambiguously attests to a noncentrosymmetric structure. Polarized Raman spectra of both isomorphous compounds have been measured and normal mode calculations performed at the Brillouin zone center. A very good agreement between observed and calculated wa venumbers has been obtained and allows all optical modes to be assigne d. The optical vibrations have been described in terms of the potentia l energy distribution and of the Cartesian displacements of the atoms. (C) 1997 Academic Press.