Electronic structure of some 3D transition-metal pyrites

Bremsstrahlung Isochromat spectra of FeS 2 , NiS 2 NiS 1.2 Se 0.8 and NiSe 2 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 FeS 2 band structure calculations are also presented; these are in good agreement with experiment. The authors show that it is necessary in this calculation to include 'empty spheres' when using a muffin-tin approximation. This is because the pyrite crystal structure is far from close packed. Furthermore, they briefly discuss the electrical and magnetic properties of the compounds.