Chalcides and pnictides of group VIII transition metals: Far-infrared spectroscopic studies on compounds MX 2, MXY, and MY 2 with pyrite, marcasite, and arsenopyrite structure

Abstract

The far-infrared (FIR) spectra of pyrites, marcasites and loellingites, and arsenopyrites of the type MX2, MY2, and MXY with M=Fe, Co, Ru, Rh, Os, Ir X=S, Se, Te, and Y=P, As, and Sb have been studied, including group theoretical treatment of the phonon modes. The internal Y - Y and X - Y stretching modes, infrared (IR) allowed only in the case of the arsenopyrites, have been found to be in the range 440–490, 470–510, 450–490, 430–450 and 400–420 cm−1 for MP2, MPS, MPSe, MAsS, and MSbS type compounds, respectively. From the obtained spectra intensity weighted mean phonon frequencies, i.e. central frequencies as defined by Plendl (1961), and mass weighted ones have been calculated and interpreted in terms of the strength of the MX and MY bonds, especially comparing 3d, 4d, and 5d transition metal compounds. Method of preparation and X-ray data of the chalcides and pnictides studied are also given.