X-ray absorption near-edge spectra of transition metal disulfides FeS₂ (pyrite and marcasite), CoS₂, NiS₂ and CuS₂, and their isomorphs FeAsS and CoAsS

Metal K- and L₃-, sulfur K- and arsenic K- and L₃-edge X-ray absorption near-edge spectra of a series of metal disulfides, FeS₂ (both pyrite and marcasite), CoS₂, NiS₂, and CuS₂, and their isomorphs, FeAsS and CoAsS, are presented. The features in this region of these spectra are interpreted using band structure and molecular orbital calculations in terms of the transitions from the 1s or 2p_3/2 state to unoccupied states. The 3d transition metal L₃-edge spectra of these materials show dependence on the degree of multiplet splitting in the final state, and thus offer less information on the electronic ground state. There are substantial differences in the spectra of the isostructural materials, whereas the spectra of the isotopes pyrite and marcasite show several similarities, illustrating the dependence of near-edge region on electronic structure.