Molecular Orbital Calculations on Iron Disilicide β-FeSi2

Ab initio molecular orbital calculations were performed on two types of FeSi8 clusters forming crystalline β-FeSi2 to examine electronic states. Mulliken population analysis on both clusters shows that d-s hybridized orbitals are predominant at a low energy level and d-p hybridized orbitals gradually become predominant with increase in energy. Since d-p hybridized states close to the highest occupied MO (HOMO) level are found to be π-type antibonding for both clusters, d-p antibonding states between Fe and Si atoms are assumed to be formed near the Fermi level in actual crystalline β-FeSi2.