Structural, electronic, elastic properties and stabilities of hexagonal ZrNiAl alloy and its hydride ZrNiAlH0.67 under pressure

The structural, electronic, elastic properties and stabilities of hexagonal prototype alloy ZrNiAl and its saturated hydride ZrNiAlH0.67 are investigated using the pseudopotential plane wave method within the generalized gradient approximation (GGA). The calculated structural parameters are in good agreement with the available experimental data. Partial covalent characters on ZrNiAl and ZrNiAlH0.67 are verified by the calculations of PDOS (partial density of states) and overlap population. Band structures show both ZrNiAl and ZrNiAlH0.67 belong to metals. The elastic constants and their pressure dependences are calculated using the static finite strain technique. From the analysis of the mechanical stabilities, hexagonal ZrNiAl is unstable at higher pressure than 29.34 GPa; that its hydride ZrNiAlH0.67 is stable up to 50 GPa is similar with the experimental result of isostructural LaNiInD1.63−x. Hydrogenation not only leads to strong lattice anisotropy but also leads to strong mechanical anisotropy.