Comparative study of electronic structure of cubic and hexagonal phases of Re3W as non-centrosymmetric and centrosymmetric low-TC superconductors

The comparative study of structural properties, stability and electronic structure of cubic and hexagonal phases of the intermetallic Re3W, which have attracted recently interest as non-centrosymmetric and centrosymmetric low-TC superconductors, was performed by means of the first-principles calculations. The optimized lattice constants, cell volumes, theoretical density, formation energies and cohesive energies, as well as electronic densities of states are obtained and analyzed. We have found that the lowering of TC (as going from h-Re3W with TC ∼ 9.4 K to c-Re3W with TC ∼ 7.8 K) correlates with lowering of the near-Fermi density of states (of the mixed W 5d + Re 5d type with admixtures of (Re,W) 6s, 6p states) owing to lowering of contributions of W 5d and Re 6p states. Our estimations of average electron-phonon coupling constants λ show that these phases are near to the weak coupling limit, with some growth of constant λ for h-Re3W (λ ∼ 0.60) as compared with c-Re3W (λ ∼ 0.42).