CALCULATION OF THE SUPERCONDUCTING PARAMETER (I2) FOR HCP TRANSITION-METALS

The Fermi-surface-averaged electron-phonon interaction <I2> has been computed for 12 hexagonal-close-packed transition metals in the 3d, 4d, and 5d series. The calculations were first done with a quasiorthogonal tight-binding formalism based on Frohlich's modified tight-binding wave function. This method employed accurate Slater-Koster fits to scalar-relativistic augmented-plane-wave band structures, and scaling laws to determine gradients of Slater-Koster parameters. The second method employed the rigid-muffin-tin approximation and the augmented-plane-wave band structures. The two methods gave the same systematic trends across the series and good agreement between computed values for most elements. Differences in some cases are attributed to sensitivity of the calculation to band-structure parameters and different approximations employed. The two results were compared with empirically deduced values and other theoretical calculations. Single-atomic character, crystal structure, and the area and complexity of the Fermi surface have been found to be important in determining the behavior of <I2>.