La(TM)5 hydrides (TM = Fe, Co, Ni): Theoretical perspectives

Systematic theoretical results for La(TM)5Hn materials with TM one of the magnetic transition metals Fe, Co, or Ni are discussed. For TM = Co, Ni the antecedent LaCo5 and LaNi5 intermetallics and hydrides are well known. While no La–Fe compounds exist, LaFe5 hydrides are predicted to form by both Miedema's phenomenological model as well as by first-principles density functional theory (DFT) for several prototype crystal structures. Enthalpies of formation and saturation hydrogen contents derived from Miedema's model and DFT are compared. Our phonon calculations for LaCo5 and LaCo5H4 yield new information on their crystal structures.