Electronic structures and bonding in alloys were predicted by using a tight binding method. Two phases were identified in the alloys. These were a high-temperature face-centered cubic, and a low-temperature face-centered tetragonal structure. It was found that H absorption was a favorable process in both structures. The H at tetrahedral interstitial sites of the face-centered tetragonal structure was 2.2eV more stable than was an impurity atom located at an octahedral interstitial site in the face-centered cubic structure. The density-of-states curves exhibited a peak below the d metal band which was made up mainly of H-based states (>50% H1s) while the metal contribution included mainly s and p orbitals. In the face-centered cubic structure, both Fe–H and Pd–H bonds developed. The Fe–Pd interface exhibited antibonding filled states near to the Fermi level. When the face-centered tetragonal phase was considered, the Fe–H overlap population decreased, while the Pd–H remained similar to the previous case. The Fe–Fe overlap population decreased and the Pd–Pd bonds were almost unaltered. The interfacial Fe–Pd bonds were almost unaffected by H.

The Effect of Interstitial Hydrogen on the Electronic Structure of Fe–Pd Alloys. E.A.Gonzalez, P.V.Jasen, N.J.Castellani, A.Juan: Journal of Physics and Chemistry of Solids, 2004, 65[11], 1799-807