Structural variations and hydrogen storage properties of Ca5Si3 with Cr5B3-type structure

Upon hydriding Ca5Si3 with a Cr5B3-type structure, the hydrogen absorption equilibrium was first attained with formation of stuffed Ca5Si3H(D)0.53 (I4/mcm) with H exclusively located in Ca4-tetrahedral sites and symmetry unchanged; with increasing pressure or temperature, more hydrogen was absorbed into the system, leading to the dissociations into CaH2 (amorphous hydride at high pressure) and CaSi. Such structure variations upon hydrogenation regarding pressures and temperatures were for the first time observed in any of A5Tt3-type intermetallic compounds.