Peculiarities of band structure in bivalent rare earth monosulfides

Total and local partial densities of states in rare-earth (SmS, EuS, YbS) monosulfides were calculated by the Green function method. Calculational results are compared with the x-ray and x-ray electron spectroscopy data. It is established that in YbS and EuS in comparison with SmS a band of metal f-states moves away from the conductivity band bottom thus increasing the energy-gap width. It is concluded with provision for value of charge transfer between sulfur and REE atoms that chemical bond in REE monosulfides is not purely ionic