Equation of state of palladium hydride and deuteride to 100 GPa

To study the behavior of palladium hydrides under pressure, we loaded palladium foils in hydrogen or deuterium environments in two separate diamond anvil cells. We subsequently measured x-ray diffraction up to 100 GPa at room temperature. No structural phase transition was observed for either PdD$_{\mathrm{x}}$ or PdH$_{\mathrm{x}}$ between 0 GPa and 100 GPa. The pressure-volume data were fitted with the third-order Birch-Murnaghan equation of state, which gave an initial volume of 10.8 cm$^{\mathrm{3}}$/mol, a bulk modulus of 153 GPa, and its derivative of 4.3 for palladium hydride. An initial volume of 10.6 cm$^{\mathrm{3}}$/mol, a bulk modulus of 162 GPa, and its pressure derivative of 4.6 were determined for palladium deuteride. From initial volumes, we conclude that x$=$1 for both PdD$_{\mathrm{x}}$ and PdH$_{\mathrm{x}}$. This work is supported by the Carnegie-DOE Alliance Center.