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.