Electronic structure and Fermi surfaces of the superconductive A3B compounds: AÂ = Â V, Nb; BÂ = Â Ga, Ge and Sn

The full-potential linearized augmented-plane wave (FP-LAPW) method is employed in calculations of the band structure and Fermi surfaces of the superconductive A15 (Cr3O-type) compounds V 3B and Nb3B, B=Ga, Ge and Sn. A plot of the total density of states shows a minimum above EF in all studied compounds separating bonding bands from antibonding bands. The V compounds possess higher densities of states at EF, whereas narrower bandwidths are observed for the Nb compounds. From the results it is inferred that the higher transition temperature Tc experimentally observed for the Nb compounds arises from larger volumes of the Fermi surfaces for electron sheets besides the multi-Fermi-surface structure.