A model for atomic hydrogen–bimetal interactions

The adsorption of atomic H on the bimetallic FeNi(111) surface has been studied by ASED-MO tight binding calculations. The energy of the system was calculated by the atom superposition and electron delocalization molecular orbital (ASED-MO) method. Seven H locations on the alloy surface were selected and the hydrogen atom was positioned in their energy minima configurations.By ASED-MO calculations, the H atom presents its most stable position when it bonds on top Fe atom at 1.5 Å and, on bridge Fe–Fe at 0.7 Å, respectively. In these cases, the strength of the local Fe–Fe bond decreases 12% and 33% of its original bulk value, respectively. As a consequence of Fe–H interaction, a decohesion mechanism in the Fe–Fe bond could be evidenced. On the other hand, the Fe–Ni and Ni–Ni superficial bonds are slightly modified between 0.4 and 2%. A discussion based on electronic structure studies using the concept of density of states (DOS) and crystal orbital overlap population (COOP) curves is presented.