Semi-empirical atom superposition and electron delocalization molecular orbital theory was used to study H-Fe interactions near to an Fe vacancy. The calculations were carried out by using clusters of the form, Fe86, and by simulating the absorption of a H atom near to a vacancy which was located at the center of the cluster. The formation of H-H pairs was also considered. The results indicated that the H-Fe interaction usually became stronger when the H atom was close to the vacancy; but not at its center. This was attributed to a strong indirect interaction that was mediated by the Fe matrix. Minima were found at eccentric positions. A H-H pair was suggested to be formed near to the vacancy region. Relaxation of first-neighbor Fe atoms towards the vacancy was considered in the presence and absence of H. In all of the situations which were studied, the most stable configuration corresponded to cluster contraction.

A Computational Study of H-Fe Vacancy Interaction C.Pistonesi, A.Garcia, G.Brizuela, A.Juan: Journal of Physics D, 1998, 31[5], 588-94