The bonding of H---Fe was analyzed by performing qualitative electronic calculations within the framework of the atom superposition and electron delocalization orbital cluster method. The changes in the electronic structure of body-centered cubic Fe, upon introducing a screw dislocation, were compared with Fe surfaces. A comparison was drawn with H adsorption at the Fe (¯112) surface, and H absorption in bulk Fe containing a dislocation. The results suggested that the detrimental effect of H upon the Fe---Fe bonds in a screw dislocation was almost half as severe as in other defects; such as an edge dislocation or vacancy. It was also limited to its first-nearest neighbor. An analysis of the orbital interaction revealed that Fe---H bonding mainly involved the Fe 4s and H 1s orbitals. When H was in the bulk, the region near to the screw dislocation core was much more repulsive than it was in a normal Fe lattice. These results suggested that H accumulation would be less favorable near to a screw dislocation than to an edge dislocation.

Electronic Structure and Bonding of Hydrogen in a Screw Dislocated BCC Fe. A.Juan, B.Irigoyen, S.Gesari: Applied Surface Science, 2001, 172[1-2], 8-17