First-principles calculations on the electronic structure of FeS

Spin-polarized first-principles band structure calculations have been performed for antiferromagnetic FeS. The experimental band gap of 0.04 eV is not opened in the local spin density approximation (LSDA) density of states but a marked dip appears at the Fermi energy located within the t_2g minority subband. The result is a consequence of the octahedral surroundings which split the minority t_2g states into one low-lying state and two degenerate states higher in energy. The dip can be enlarged to a small gap for very low U values when the Hubbard correction is employed. The calculated magnetic moment of 3.5μ_B is close to the value of 4μ_B deduced from the ionic model. The density of states (DOSs) compares satisfactorily with the photoemission and bremsstrahlung isochromat spectroscopy (BIS) spectra.