The electronic structure and location of H pairs in bcc Fe edge dislocation

The H±Fe interaction near an edge dislocation line was studied using qualitative electronic calculations in the framework of the atom superposition and electron delocalisation molecular orbital (ASED-MO) theory. Calculations were performed using a Fe207 cluster to simulate a dislocated bcc structure. The cluster geometry and atomic parameters were optimised to make a better approximation to the repulsive energy terms. The ®nal localisation of two H atoms inside the cluster were determined as they entered from the (0 0 1) surface. The results indicate that the H±Fe interaction is stronger near the dislocation, making it a possible region for H accumulation. Changes in the electronic structure of bcc dislocated Fe were analysed for the system without H, with one H atom and with two H atoms. Fe atoms surrounding the dislocation line which are initially more strongly bonded with each other than the bulk Fe atoms weaken their bond when H is present. This is due to the formation of an H±Fe bond. H in¯uences only its nearest Fe atoms. The H±H interaction was also analysed. # 2001 Published by Elsevier Science B.V.