THE EFFECT OF INTERSTITIAL HYDROGEN ON THE ELECTRONIC STRUCTURE OF THE B2 FeAl ALLOY

ESTELA GONZALEZ; PAULA JASEN; GRACIELA BRIZUELA; RISTO NIEMINEN; ALFREDO JUAN

PHYSICA STATUS SOLIDI B-BASIC RESEARCH

WILEY-V C H VERLAG GMBH

Año: 2007 vol. 244 p. 3684 - 3694

0370-1972

The electronic structure and bonding in a B2 Fe-Al alloy with and without hydrogen as an  interstitial atom were computed using a tight binding theoretical method. The hydrogen absorption turns out to be a favorable process. The hydrogen was found near an Al octahedral site, the Al-H distance being shorter than that of Fe-H.             The density of states (DOS) curves show several peaks below the d metal band which is made up mostly of hydrogen based states (>50% H 1s) while the metal contribution includes mainly s and p orbitals.  An electron transfer of nearby 0.14e- comes from the metal to the H. The overlap population values reveal metal-metal bond breaking, the intermetallic bond being the most affected. The H bond mainly with the Al atoms and the reported Fe-H overlap population is much lower than that corresponding to FePd alloys and BCC Fe. The changes in the overlap population show the Fe-Al bond is weakening nearly 53 % after H absorption, while the Fe-Fe bond is only weakened 23%.