Synthesis of ruthenium hydride

Ruthenium hydride was synthesized at a hydrogen pressure of about 14 GPa in a diamond-anvil cell. Energy-dispersive x-ray diffraction was used to monitor the ruthenium crystal structure as a function of hydrogen pressure up to 30 GPa. The hydride formation was accompanied by phase transition from the original hcp structure of the pristine metal to the fcc structure. Our results confirmed the theoretical prediction of ruthenium hydride formation under hydrogen pressure. The standard Gibbs free energy of the ruthenium hydride formation reaction was calculated assuming the pressure of decomposition as the equilibrium pressure.

Figure 1

Energy dispersive x-ray diffraction patterns of ruthenium as a function of hydrogen pressure taken during pressure increase. For clarity only selected patterns are presented here. The scattering angle corresponds to $Ed=34.8\mathrm{keV}\AA$.

Figure 2

Energy dispersive x-ray diffraction patterns of ruthenium as a function of hydrogen pressure taken during pressure decrease. The scattering angle corresponds to $Ed=34.9\mathrm{keV}\AA$.

Figure 3

Pressure-volume relationships for the ruthenium-hydrogen system (symbols and black curves) and pure ruthenium (blue curve) [27]. The solid triangles denote compression data, and the empty ones indicate decompression. The left $Y$ axis corresponds to the volume calculated per one metal atom, and the right axis shows molar volumes.