Changes in electronic,magnetic and bonding properties from Zr2FeH5 to Zr3FeH7 addressed from ab initio

Potential hydrogen storage ternaries Zr₃FeH₇ and Zr₂FeH₅, are studied from ab initio with the purpose of identifying changes in electronic structures and bonding properties. Cohesive energy trends: E_coh. (ZrH₂) > E_coh. (Zr₂FeH₅) > E_coh. (Zr₃FeH₇) > E_coh. (hypothetic-FeH) indicate a progressive destabilization of the binary hydride ZrH₂ through adjoined Fe so that Zr₃FeH₇ is found less cohesive than Zr₂FeH₅. From the energy volume equations of states EOS the volume increase upon hydriding the intermetallics leads to higher bulk moduli B₀ explained by the Zr/Fe–H bonding. Fe–H bond in Zr₂FeH₅ leads to annihilate magnetic polarization on Fe whereas Fe magnetic moment develops in Zr₃FeH₇ identified as ferromagnetic in the ground state. These differences in magnetic behaviors are due to the weakly ferromagnetic Fe largely affected by lattice environment, as opposed to strongly ferromagnetic Co. Hydrogenation of the binary intermetallics weakens the inter-metal bonding and favors the metal–hydrogen bonds leading to more cohesive hydrides as with respect to the pristine binaries. Charge analyses point to covalent like Fe versus ionic Zr and hydrogen charges ranging from covalent H^?0.27 to more ionic H^?0.5.