Superconducting and optical properties of α-zirconium from its augmented-plane-wave band structure

Abstract

The detailed electronic energy band structure of hexagonal close-packed alpha -zirconium, corresponding to the atomic configuration 4d25s2 of its four outermost valence electrons, has been computed by the composite-wave variational version of the augmented-plane-wave (APW) method in conjunction with the X alpha ( alpha =0.70424) exchange approximation for obtaining the potentials. From these data the electronic density of states and its angular-momentum-decomposed components have been obtained by the Raubenheimer-Gilat method. These quantities are required in order to calculate the electron-phonon interaction parameter ( lambda ) and the superconducting transition temperature (Tc) within the framework of the theories of Gaspari and Gyorffy (1972) and McMillan (1968). A study of the variation of Tcd with the Coulomb pseudopotential ( mu *) revealed that mu *=0.1 yields the best agreement between theory and experiment for alpha -Zr. Also studied from the energy band data are the optical properties of alpha -Zr via the variation of the imaginary part of the interband dielectric function for bound electrons and the corresponding optical conductivity ( sigma ) as a function of the photon energy ( omega ). The results indicate five peaks in the sigma - omega curve, the positions of which on the energy scale in fair agreement with experiment.