Electronic and optical properties of Fe, Zn and Pb sulfides

Ab initio quantum-chemical calculation of the spatial and electronic structures of sphalerite (ZnS), pyrite (FeS 2) and galena (PbS), using the density functional theory (DFT) local density approximation (LDA) and generalised gradient approximation (GGA), the Hartree-Fock (HF) method and the hybrid functional B3LYP, have been carried out. The calculated density of states (DOS) for the conduction band is used to interpret the experimental features of the S 1s X-ray absorption near-edge structure (XANES) spectra obtained using synchrotron radiation. Because of the Δ l = ±1 selection rule for electron excitation, the S K-edge XANES spectra represent a transition of the S 1s electron to conduction band S p-like orbitals. The peak positions observed experimentally in the near-edge region, up to 15 eV past the edge are approximated well by the conduction band S p DOS for sphalerite and galena. For pyrite a better approximation of the XANES data is achieved if peak assignments are made to a mixture of S p and Fe p and d conduction band states.