Electronic, superconducting, and optical properties of technetium from its augmented-plane-wave band structure

The detailed energy-band structure of hexagonal-close-packed technetium, corresponding to the atomic configuration 4d/sup 5/5s/sup 2/ of its seven outermost valence electrons, has been obtained throughout the Brillouin zone using the composite-wave variational version of the augmented-plane-wave (APW) method in conjunction with the X..cap alpha.. (..cap alpha.. = 0.702 99) exchange approximation for obtaining the potentials. From the band-structure data the electronic density of states (DOS) and the angular-momentum--decomposed DOS were calculated by the accurate Gilat-Raubenheimer method. These quantities were used to calculate the electron-phonon coupling constant and the transition temperature (T/sub c/) using the theories of Gaspari and Gyorffy and of McMillan. Also studied were the Fermi surface and the optical properties of Tc via the imaginary part of the interband dielectric constant for bound electrons, the latter being the first of such a study on Tc to date. The superconducting properties and the Fermi surface which could be compared to experiments show, in general, satisfactory agreement.