Systematics for trivalent and divalent rare-earth sulphides

The electronic structures of the rare-earth monosulphides are calculated with

the self-interaction corrected local-spin-density approximation. This scheme

allows part of the rare-earth f shell to be localized. Both trivalent and divalent

configurations of the rare earths are considered, and the systematics in lattice

constants and electronic densities of states are investigated. The scheme is found

to be accurate in describing the properties of these systems and reveals that two

kinds off electrons in fact are present in the rare-earth monosulphides, namely

both localized atomic-like f electrons and itinerant band f electrons, which

hybridize with the normal conduction bands. The stability of the divalent

configuration directly correlates with the number of band f electrons.