Electronic Structure And Fermi Surface Of The Superconductors Lanibio And Lacubio From First Principles

Based on first-principle full-potential linearized augmented plane wave generalized gradient approximation calculations, we have investigated electronic structure of synthesized superconductors LaMBiO, where M=Ni or Cu as examples of bismuth-containing compounds in the family of superconducting quaternary oxypnictides. The band structure, density of states, and Fermi-surface features are discussed. Our results indicate that chemical bonding inside La-O and M-Bi layers is covalent while the interlayer binding is mostly ionic. The states of M-Bi layers are found to prevail at the Fermi level. The corresponding Fermi surfaces bear a two-dimensional character thus suggesting strongly anisotropic conduction mostly via M-Bi layers. On the whole, the oxybismuthides may be described as superconducting nonmagnetic ionic metals.