Electronic structure and electron-phonon coupling in stoichiometric and defective hydrides MPdH(3) (M=Ca, Sr, Eu, Yb)

On the basis of electron transfer from the divalent element to the PdH3 entities, the perovskite structure MPdH(3) (M=Sr, Eu, Yb) are expected to have similar electronic states at the Fermi energy as superconducting Pd-H-x and Pd-noble-metal-H-x and thus could be potential candidates for superconductivity. With this motivation, we have investigated the electronic structure and some aspects of the electron-phonon coupling in these hydrides using the nb initio augmented plane-wave method, and the results of the energy bands, the total and partial wave analysis of the density of states, and the electronic contribution, eta(H) to the electron-phonon coupling are presented. Similar studies for the hydrogen defective material CaPdH2 are also included. We have found that all these compounds are metallic with essentially filled Pd-d bands and a small density of states at Fermi level as in PdH. Nevertheless, the calculated values of eta(H), which govern the contribution of the hydrogen atoms to the electron-optical phonon coupling parameter lambda, although sizeable, are lower than in PdH. This would indicate that these compounds, if superconducting, would have lower values of the superconducting transition temperatures T-c than in PdH.