The electronic structure and bonding of a H–H pair in the vicinity of a BCC Fe bulk vacancy

The H–Fe interaction near a bcc Fe vacancy is analysed using a semi-empirical theoretical method. Calculations were performed using a Fe86 cluster with a vacancy. Hydrogen atoms are positioned in their local energy minima configurations. s in the electronic structure of Fe atoms near a vacancy were analysed for the system without H, with one H and with two H atoms. Fe atoms surrounding the vacancy weaken their bond when hydrogen is present. This is due to the formation of H–Fe bonds. Hydrogen influences only its nearest-neighbour Fe atoms. The H–H interaction was also analysed. For H–H distance of 0.82 Å an H–H association is formed, while H–Fe interaction and Fe–Fe weakening is markedly reduced, when compared with other H–H interactions.