Electronic structure and hyperfine interactions in tetrahedral alkali-dithioferrates (III) as calculated by the multiple-scattering method

Spin-polarized multiple scattering and the Slater $X\alpha$ local exchange calculations have been performed on the tetrahedral cluster Fe${\mathrm{S}}_4^{5-}$. The calculated charge and spin densities at the Fe nucleus have been used to interpret the Mössbauer hyperfine parameters. Iron $3d$ and $4s$ populations were used to explain the large reduction of the free-ion Fermi contact term as well as the $4s$ contribution. The calculated number of unpaired $3d$ electrons agrees very well with magnetic susceptibility measurements. From the calculated energy levels, electronic transitions in the optical spectrum have been assigned.