Band structure and semiconducting properties of FeSi

The semiconductor-type band structure characteristics of FeSi are presented. The results of linear augmented-plane-wave band calculations for cubic FeSi predicted a small (approx0.11 eV) indirect semiconductor gap that agreed well with the empirical estimates (approx0.13 eV). The calculations were carried out in the local-density approximation (LDA). The origin of this gap, that occurred within the Fe(3d) manifold, could be traced to a pseudogap present in the reference rocksalt phase that underlay the lower-symmetry FeSi structure. The relationship between the FeSi band structure and several types of many-body correlation mechanisms which were used to explain its anomalous temperature-dependent magnetic properties, is discussed. The unusual temperature dependence of the magnetic susceptibility of this compound was not accounted for by the LDA density of the states results.