Electronic properties ofNb3Ge andNb3Al from self-consistent pseudopotentials. I. Band structure and density of states

Abstract

The self-consistent-pseudopotential method is applied to the $A-15\mathrm{}$ compounds ${\mathrm{Nb}}_3$Ge and ${\mathrm{Nb}}_3$Al. The Fermi energy is found to lie in a region of very flat bands having a bonding character along the Nb chains. Comparison with the band structures of the (nonexistent) $A-15\mathrm{}$ materials ${\mathrm{Nb}}_3$Nb and ${\mathrm{Nb}}_3$ (chains only) suggest that the $p$ states on the Ge and Al atoms are instrumental in determining the position of the Fermi level. There is little evidence for rigid-band behavior in the ${\mathrm{Nb}}_3{\mathrm{Al}}_x{\mathrm{Ge}}_{1-x}$ system. Studies of the effects of chain dimerization in ${\mathrm{Nb}}_3$Ge suggest that states at $R$ and $M$ are more likely candidates to participate in structural transitions than states at $\Gamma$ or $X$.