The electronic structure and bonding in a B2 Fe-Al alloy with and without H as an interstitial atom were studied within the framework of the density functional theory and the findings compared with previous results in Fe an Al. The H absorption turned out to be a favourable process. The H was found near to an Al octahedral site, the Al-H distance being shorter than that of Fe-H. The density of states curves showed several peaks below the d metal band which was made up mostly of H based states (>50%H1s) while the metal contribution included mainly s- and p-orbitals. An electron transfer of nearby 0.14e- came from the metal to the H. The overlap population values revealed metal-metal bond breaking, the intermetallic bond being the most affected. The H bonded mainly with the Al atoms and the reported Fe-H overlap population was much lower than that corresponding to FePd alloys and body-centred cubic Fe. The changes in the overlap population showed the Fe-Al bond was weakened by nearly 53% after H absorption, while the Fe-Fe bond was only weakened by 23%.

The Effect of Interstitial Hydrogen on the Electronic Structure of the B2 FeAl Alloy. E.A.González, P.V.Jasen, G.Brizuela, A.Juan, R.Nieminen: Physica Status Solidi B, 2007, 244[10], 3684-94