Structural and hydrogen sorption properties of SmNi5−xGax system – an experimental and theoretical study

• A series of SmNi5−xGax intermetallic compounds is synthesized and characterized.
• Hydrogen desorption was followed by pressure–composition isotherms.
• Thermodynamic parameters and hydrogen capacity were determined.
• Enthalpies of hydrogen absorption are obtained by DFT.
• Hydrogen sorption was discussed with respect to positions of Ga in intermetallic lattice.

A series of ternary alloys of general formula SmNi5−xGax (x = 0.25, 0.5, 1.5, 2, 2.5) was prepared by melting mixtures of Sm, Ni and Ga in arc furnace under argon. From X-ray powder diffraction lattice parameters are determined and it is found that hexagonal structure of P6/mmm space group is retained for all considered values of x. Hydrogen absorption ability and thermodynamic quantities of the systems are determined by pressure-composition desorption isotherms. The obtained properties are compared with those of previously reported SmNi5 and SmNi4Ga. DFT calculations were performed for selected members of the system and the results are discussed with regard to experiment.