The crystal and electronic structure of CaPd3H

A new calcium substituted palladium hydride, CaPd3H, has been synthesized a nd the metal structure was found to be of the Ni3Ti (D0(24)) type. From a G uinier-Hagg X-ray powder diffraction pattern the unit cell dimensions were determined to be a = 5.8617(2) and c = 9.7793(6) Angstrom. Resistance measu rements did not reveal any superconducting transition, but the alloy has me tallic character. From considerations of bonding distances in the binary hy drides, the hydrogen atoms are restricted to the octahedral site coordinate d by six palladium atoms. The experimental results were confirmed by theore tical calculations on the electronic structure, using the LMTO method. The d-electron bands are filled at the CaPd3H composition, thus limiting the hy drogen occupancy to only one H atom per formula unit. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.