Density functional study of H–Fe vacancy interaction in bcc iron

The Fe-H interaction in the vicinity of a vacancy in bcc iron was studied within the framework of the density functional theory and the findings compared with previous results obtained by semiempirical molecular orbital methods. Calculations were performed using an iron cluster containing 12 atoms and a vacancy. Geometry optimizations were performed to find the most stable positions for one and two hydrogen atoms. Changes in the electronic structure of Fe atoms near the vacancy were analysed when one and two H atoms are added to the iron cluster. Fe atoms surrounding the vacancy weaken their bond when hydrogen is present. This is interpreted in terms of the formation of Fe-H bonds.