The electronic structure and bonding of an hydrogen pair near a FCC Fe stacking fault

The bonding of H to Fe is analyzed using qualitative electronic calculations in the framework of the atom superposition and electron delocalization orbital cluster method (ASED–MO). Upon introduction of a stacking fault in FCC Fe, the changes in the electronic structure are studied when a pair of hydrogen atoms are located near the fault. A cluster of 180 metallic atoms distributed in five layers represents the solid. The interstitial H atoms are positioned in accordance with previous studies. The Fe–H interaction decreases the Fe–Fe bond strength and the H effect is limited to the first Fe neighbor. An analysis of the orbital interaction reveals that the Fe–H bonding involves mainly the Fe 4s and H 1s orbitals. The orbital population analysis reveals some H–H association, which is more important than that obtained in dislocated Fe. A comparison is given with H pairs located near BCC Fe dislocations or vacancies.