ELECTRONIC BAND-STRUCTURE OF SULFIDE SPINELS CUM(2)S(4) (M=CO, RH, IR)

Full-potential linearized augmented-plane-wave band calculations based on the local density approximation are performed for three sulphide s pinels CuM(2)S(4) (M = Co, Ph, Ir). The electronic states near the Fer mi level consist mainly of the M nd epsilon (n = 3 for Co, 4 for Rh, 5 for Ir) and the S 3p orbitals. A large d gamma-d epsilon splitting of the M nd bands is attributed mainly to the effects of hybridization b etween the M nd gamma and the S 3p orbitals. The Co 3d orbitals are mo re localized compared with the Ph 4d and the Ir 5d orbitals. Among the three compounds, the density of states or the partial density of stat es of the M nd components at the Fermi level is largest in CuCo2S4. Th e 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 ion s is Cu1+ rather than Cu2+. Hence the Cu ions are expected to be non-m agnetic.