The high-pressure lithium-palladium and lithium-palladium-hydrogen systems.

ABSTRACT

The lithium-palladium and lithium-palladium-hydrogen systems are investigated at high pressures at and above room temperature. Two novel lithium-palladium compounds are found below [Formula see text]. An ambient temperature phase is tentatively assigned as [Formula see text], with [Formula see text] Å at 8.64 GPa, isostructural with [Formula see text]. The other phase occurs at high-temperature and is [Formula see text], [Formula see text] Å at 3.88 GPa and 200 [Formula see text], similar to [Formula see text], which is also known at high pressure. The presence of hydrogen in the system results in an [Formula see text] structure with [Formula see text] Å at 9.74 GPa. This persists up to [Formula see text], the highest pressure studied. Below [Formula see text] an fcc phase with a large unit cell, [Formula see text] Å at 0.39 GPa, is also observed in the presence of hydrogen. On heating the hydrogen containing system at 4 GPa the [Formula see text] phases persists to the melting point of lithium. In both systems melting the lithium results in the loss of crystalline diffraction from palladium containing phases. This is attributed to dissolution of the palladium in the molten lithium, and on cooling the palladium remains dispersed.