The role of the Coulomb gap in the self-consistent band structure of SmS

Abstract
The electronic structure of SmS is determined by means of a self-consistent APW calculation which includes both the occupied and the unoccupied 4f bands. The Coulomb splitting gives rise to the semiconducting phase in this Sm compound as well as the hybridisation of the empty 4f orbitals with with other extended states in the conduction band. Another calculation is performed that involves reducing the crystal volume by up to 0.87 V, where-upon a metallic phase appears because the occupied 4f bands are mixed with the conduction band.