Open Access Conference Proceedings

The La-Ni binary system, and in particular the LaNi5 binary intermetallic phase, has been intensively studied in recent decades, especially as a promising hydrogen storage material. Knowledge of phase equilibria is very important for the possible optimization of material properties. This work is focused on the study of the thermodynamic properties of the La2Ni7 phase, which occurs in phase equilibrium with the LaNi5 phase and can therefore influence the capacity and dynamics of these hydrogen storage materials in real materials. The alloy samples were prepared from pure elements using a gravity melting furnace in an inert Ar-6N atmosphere. The overall composition and chemical composition of the phases were analyzed by SEM-EDX. The crystal structure of the phases was confirmed by powder XRD. Our experiments were complemented by quantum-mechanical calculations implementing the density functional theory (DFT) within the generalized gradient approximation (GGA) to determine the ground-state structural, electronic, thermodynamic, and elastic properties of La2Ni7. A computational unit cell of La2Ni7 contains 36 atoms and has a strongly anisotropic shape. The computed results obtained for static lattices indicate that La2Ni7 is thermodynamically stable with respect to the decomposition into elemental end members. The stress-strain method was used to address the mechanical stability by computing a full tensor of the second-order elastic constants and La2Ni7 has been found to be mechanically stable.

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