Electronic structure of some 3D transition-metal pyrites

Abstract

Bremsstrahlung Isochromat spectra of FeS2, NiS2, NiS1.2Se0.8 and NiSe2 are reported. These are the first direct experimental evidence for a sharp antibonding p-like state above the Fermi level. A comparison is made with experimental results in the literature. For FeS2, band-structure calculations are also presented; these are in good agreement with experiment. We show that it is necessary in this calcualtion to include 'empty spheres' when using a muffin-tin approximation. This is because the pyrite crystal structure is far from close packed. Furthermore, we briefly discuss the electrical and magnetic properties of the compounds.