Electron momentum distribution in Pd and PdH

Abstract

The electron momentum distributions (EMD's) in Pd and stoichiometric PdH have been calculated using the augmented-plane-wave (APW) method. It is shown that total EMD as well as the partial EMD contributed by the individual bands change significantly in going from Pd to PdH. These differences are discussed in terms of the changes in the energy bands of Pd upon the introduction of hydrogen. The EMD of PdH calculated by the APW method is compared with that obtained with a rigid-band approximation to bring out the limitations of the rigid-band approximation. Although the Fermi surface of PdH shows a qualitative agreement with that of Ag, the EMD of PdH is quite different from that of Ag. The calculated EMD's are used to obtain the difference between the Compton profiles from polycrystalline PdH_0.72 and Pd and the results are compared with experiment.