Single crystal raman studies of pyrite-type RuS2, RuSe2, OsS2, OsSe2, PtP2, and PtAs2

Single crystal Raman spectra of pyrite-type RuS₂, RuSe₂, OsS₂, OsSe₂, PtP₂, and PtAs₂ are presented and discussed with reference to the energies of the X-X stretching modes _x-x (A _g, F _g) and the X₂ librations (E, 2F_g). The main results obtained are (i) strong Raman resonance effects, (ii) different sequences for _x-x (A _g) and (E _g), i.e., for PtP₂ and PtAs₂ and for OsS₂, owing to the interplay of intraionic and interionic lattice forces, (iii) greater strengths for the intraionic P-P and As-As bonds compared to the S-S and Se-Se bonds, respectively, and (iv) a strong influe_gnce of the metal ions on the strength of the X-X bonds.This is contribution LXI of a series of papers on lattice vibration spectra