Bonding and electronic structure of superconducting NbPS

Tight-binding band structure calculations performed on the structure of niobium phosphide sulfide are analyzed. The bonding of the linear semicontinuous chain of P atoms present in this material is analyzed with a two-dimensional model; a Nb-P interaction that disrupts the σ bonding within the chain leads to the observed P-P distances. A crystal orbital centered on the Nb atoms that is nonbonding with the P and S atoms in segments of the Brillouin zone affords a peak in the density of states at the Fermi level that is correlated with the observed high superconducting transition temperature. The metal-to-metal bonding is examined, and the structures and physical properties of some postulated compounds are anticipated