Effect of hydrogen pair in an iron-nickel alloy embrittlement

Computational calculations have been performed to study the location of two hydrogens in a vacancy zone of a Fe50Ni50 cell. H debilitates the original metal-metal bonds by forming strong interactions with local Fe atoms. H-metal exchange contributes to the absorption process. The interactions mainly involve 4 s and 4p metal atomic orbitals. The bond strength of Fe-Fe, Fe-Ni, and Ni-Ni, nearest neighbors to H, decreases to about 60%, 33%, and 20%, respectively, with the Fe-Fe bond as the most affected. The net H-H interaction is almost null; H2 molecule is not formed in the vacancy zone of the Fe50Ni50 cell.