Density Functional Theory study of the hydrogen storage in a vacancy zone of an iron-nickel cell

Calculations using the SIESTA code have been performed to study the location of one and two hydrogens in a vacancy zone of a Fe50Ni50 cell. H debilitates the original metal-metal bonds by forming strong interactions with the metallic matrix. The Fe-H interaction is stronger than the Ni-H interaction. The H-metal exchange contributes to this process. After first H atom adsorption, the strength of the nearest Fe-Fe, Fe-Ni and Ni-Ni bonds decreases to about 89%, 15% and 1%, respectively. Then, the Fe-Fe bond is the most affected. The adsorption of an additional H atom modified the metal-metal strength in a lesser percent. Then, no additional decohesion is observed in the metallic bonds when two H atoms are present but in this case more metallic bonds are affected. The H-H interaction is small; an H2 molecule is not formed in the vacancy zone of the Fe50Ni50 cell.