Accurate heat of formation for fully hydrided LaNi5 via the all-electron full-potential linearized augmented plane wave approach

The heat of formation, Δ Hf, for La2 Ni10 H14, an important property for hydrogen storage, was remarkably overestimated in calculations, and has discouraged the use of first principles total energy methods in the search for novel metal hydrides. Here, we employ the all-electron full-potential linearized augmented plane wave method within both the generalized gradient approximation (GGA) and the local density approximation (LDA), along with a unique treatment of the total energy of the H2 molecule, which plays a critical role in Δ Hf determinations. The calculated electronic properties indicate that charge transfer from the interstitial region to the H atoms stabilizes LaNi5 hydride. We find the calculated Δ Hf (-31.3 kJ mol H 2) within GGA is in excellent agreement with experiment (∼-32 kJ mol H 2), as are the predicted geometrical structures for LaNi5 and La2 Ni10 H14. Surprisingly, although LDA calculations underestimate the volume of LaNi5 by 10.4%, the final value of Δ Hf (-31.2 kJ mol H 2), is also in excellent agreement with experiment.