The crystal structure of a new triclinic ternary phase: τ3-Cr4(Al, Si)11

The hydrogenation at different temperatures and hydrogen pressures of the binary intermetallic compound CeNi was studied. A hydride with the composition CeNiH2.9(1) was obtained by hydriding the host alloy at 293 K and PH2=1 MPa. With increasing temperature of hydriding a reaction of hydrogenolysis of CeNi occurred with formation of a stable two-phase product composed of CeH2.51 and CeNi5. The newly prepared hydride CeNiH2.9(1) was found to be isostructural with CeNi (orthorhombic, CrB-type, S.G. Cmcm). On the basis of refinement of the XRD patterns of both the intermetallic compound and its hydride, the atomic positions of Ce and Ni and the interatomic distances were determined. The probable sites of hydrogen intersection in the host structure were proposed. Moreover, a valence transition of cerium from intermediate valence (CeNi) to the trivalent state (CeNiH2.9) was evidenced by magnetization measurements.