Band structure and superconductivity ofPdDxandPdHx

Abstract

A study of the electronic band structure of the pailadium-hydrogen system was made using the augmented-plane-wave method. The calculations were performed self-consistently for two choices of the exchange parameters within the $X\alpha$ scheme. Spin-independent relativistic corrections were included explicitly. The results for the energy bands are compared with previous calculations. Our results are found to be in good agreement with photoemission measurements. The calculations of the superconducting properties of this system are studied as a function of hydrogen content, utilizing the theory of Gaspari and Gyorffy and neutron-scattering data. The results for the superconducting transition temperature $T_c$ are in very good agreement with the measured values. An analysis of these results attributes the observed inverse isotope effect to the effective increase of the Pd-H force constant over the Pd-D force constant, due to enhanced anharmonicity of the H motion, as originally proposed by Ganguly.