Cu, Fe, and S K- and L-edge XANES spectra of ${\mathrm{CuFeS}}_2:$ Localization and interpretation of pre-peak states

The pre-peak in the x-ray-absorption near-edge structure (XANES) of ${\mathrm{CuFeS}}_2$ is studied by exploring the associated photoelectron probability density as well as by investigating the cluster size effect. All significant features of the Cu, Fe, and S K-edge experimental spectra and of the S $L_{2,3}$-edge spectrum are successfully reproduced by the real-space multiple-scattering (RSMS) calculations with self-consistent scattering potentials and by full-potential band-structure calculations employing all-electron pseudopotentials. Pre-peak-forming photoelectron states are confined to all Fe sites of the finite cluster involved in the RSMS calculation, not just to that Fe which is the nearest one to the photoabsorbing atom. Different interpretations of the pre-peak can be unified within a single scheme of the photoelectron probability density. In order to achieve a comprehensive understanding of XANES features, both the photoelectron probability density and the cluster size effect ought to be analyzed.