First-principles study on hydrogen storage in Al-, Ca-, Mn-doped MgNi clusters

Using a density functional approach calculation, the structural and electronic properties of Mg8Ni5, Mg(8)Ni(4)A(1), Mg8Ni4Ca and Mg8Ni4Mn clusters are investigated. The Al-, Ca-, Mn-doping in MgNi clusters lengthen (d)(mg-Ni), also increase the Mulliken charge, and improve magnetic moment on most shell atoms, so that the doping is helpful for hydrogen storage. The reaction heats of hydrogenation, the enthalpies of formation, the desorption energies show that the Mg8Ni4Mn, Mg8Ni5, Mg(8)Ni(4)A(1) clusters have a good property of hydrogen storage materials with relatively higher reaction heat of hydrogenation, and that their hydrides have a smaller desorption energy. So the Mg8Ni4M (M = Ni, Al, Ca, Mn) clusters are some preferred candidates of H storage. These results indicate the advantage of small size and suitable metal-doped MgNi clusters on hydrogenation and dehydrogenation.