Hydrogenation Character and Crystal Structures of Hydrides in RMgNi<sub>4</sub> (R = Nd, Gd, Er)

Whether the pseudo-binary RNi2 compounds consistent with the criterion rA/rB = 1.37 for HIA. The hydrogenation performances and crystal structures of the pseudo-binary RMgNi4 (R = Nd, Gd, Er) were investigated at fixed R/Mg ratio equal to 1. The pseudo-binary RMgNi4 (R = Nd, Gd, Er) compounds can repetively absorb and desorb hydrogen without the occurrence of HIA and decomposition during hydrogen absorption and desorption cycles at 298 K, 6 MPa. The HIA criterion rA/rB of pseudo-binary RMgNi4 alloys should be higher than 1.37 at fixed R/Mg equal to 1.