Mechanical stability and formation analysis of Pd/Rh dihydride alloys under pressure

The mechanical stability of PdxRh1−xH2 (x = 0.25, 0.5, 0.75) under pressure up to 70 GPa was carried out by first principle calculations based on density functional theory. According to our results, Pd0.75Rh0.25H2, Pd0.5Rh0.5H2 and Pd0.25Rh0.75H2 are mechanical stable when pressure is below 43.9 GPa, 35.4 GPa and 41.2 GPa, respectively. The reaction enthalpy of PdxRh1−xH2 formation paths: PdxRh1−x + 1/2H2 = PdxRh1−xH, PdxRh1−xH + 1/2H2 = PdxRh1−xH2 were further investigated. The Pd0.75Rh0.25H2 was found to be stable in pressure interval from 28.1 GPa to 43.9 GPa. Moreover, the elastic moduli, Poisson's ratio, Debye temperature, ductility and anisotropy of PdxRh1−xH2 were further investigated based on the elastic constants.