Open Access Conference Proceedings

La-Ni compounds are considered promising candidates for future hydrogen-storage applications. Some of the La-Ni phases have been insufficiently studied so far and some critically important data are missing. In particular, the La5Ni19 intermetallic compound is reported to crystallize in either hexagonal or trigonal R3 phase, but the stability of these two variants has not been satisfactorily addressed. We have employed quantum-mechanical calculations implementing the density functional theory within the generalized gradient approximation to determine the ground-state structural, electronic, magnetic, thermodynamic, and elastic properties of the two phases. The hexagonal phase is described by a computational cell containing 48 atoms, while the trigonal phase contains 72 atoms. Both computational cells are strongly anisotropic. Static lattice calculations indicate that both phases are very similar with the hexagonal phase having a slightly lower formation energy (by less than 1 meV/atom). The computational cell volumes and the total magnetic moments are practically identical in both phases. Further, the stress-strain method proved (by computing a full tensor of the second-order elastic constants) that both phases are mechanically stable.

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