The interaction of carbon and hydrogen in a -Fe divacancy

The location of a carbon and two hydrogen atoms in a α -Fe divacancy is analysed using a tight-binding theoretical method. Calculations were performed using a Fe 124 cluster. Absorption sites for the impurities near the divacancy correspond to local energy minima configurations. Fe atoms first neighbours to H atoms weaken their metallic bonds. The decohesion of Fe–Fe bonds could be associated to H embrittlement. The C atoms almost do not affect the Fe–Fe bond strength. Fe–C and Fe–H bonds are formed mainly with Fe 4s orbitals. There is no bonding between C and H atoms but some H–H interaction is observed.