LATTICE VIBRATION-SPECTRA .65. RAMAN-SPECTRA OF MNSE2, MNTE2, RUTE2, AND OSTE2

Raman spectra (single crystals and hot-pressed samples) of pyrite-type MnSe2, MnTe2, RuTe2, and OsTe2 are presented. The five allowed first-order Raman-active phonon modes have been observed and classified. The energies of the pure X-X stretching modes (species A(g), tellurides 175-179 cm-1, MnSe2 267 cm-1) do not simply correlate to the X-X bond lengths owing to the different interplay of intraionic and interionic lattice forces on these vibrations. The energies of the X2 librations (E(g), tellurides 120-190 cm-1) reflect the metal-chalcogen bond strengths, which increase in the order Mn < Ru < Os.