Electronic band structure of sulphide spinels CuM₂S₄(M=Co, Rh,Ir)

Abstract

Full-potential linearized augmented-plane-wave band calculations based on the local density approximation are performed for three sulphide spinels CuM2S4 (M=Co,Rh,Ir). The electronic states near the Fermi level consist mainly of the M ndT (n=3 for Co,4 for Rh,5 for Ir) and the S 3p orbitals. A large d gamma -d$54T splitting of the M nd bands is attributed mainly to the effects of hybridization between the M nd gamma and the S 3p orbitals. The Co 3d orbitals are more localized compared with the Rh 4d and the Ir 5d orbitals. Among the three compounds, the density of states or the partial density of states of the M n/sub /components at the Fermi level is largest in CuCo2S4. The Cu 3d orbitals form relatively narrow bands. Judging from the number of Cu 3d electrons in the muffin-tin sphere the valence of the Cu ions is Cu1+ rather than Cu2+. Hence the Cu ions are expected to be non-magnetic.