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

Abstract

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 ν _x-x (A _g, F _g) and the X₂ librations $R_{x_2 }$ (E, 2F_g). The main results obtained are (i) strong Raman resonance effects, (ii) different sequences for ν _x-x (A _g) and $R_{x_2 }$ (E _g), i.e., $\nu _{x - x} > R_{x_2 }$ for PtP₂ and PtAs₂ and $\nu _{x - x} > R_{x_2 }$ 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.