First-principles investigations of hydrogen trapping in Y₂O₃ and the Y₂O₃|bcc Fe interface

Based on first-principles calculations, the binding energy of hydrogen atom to Y₂O₃ and Y₂O₃|bcc Fe interface (relative to bcc Fe side) with cube-on-cube orientation is at least 0.45 eV, if hydrogen substitutional is considered, or at least 0.26 eV if only hydrogen interstitial is considered. The calculated binding energies do not have a unique fixed value, because they are dependent on the interface structure, the Fermi level of Y₂O₃ near the interface and the chemical potential of Y/O. Hydrogen substitutional is more stable than hydrogen interstitial near the interface for Fermi level around calculated Schottky barrier height (SBH) at equilibrium. The Y₂O₃ particle interior can be an effective trapping site for hydrogen. Hydrogen interstitial, hydrogen substitutional and Y/O vacancy have a much lower energy near the interface than within the Y₂O₃ particle, presumably due to image charge interaction related to their non-zero charge state. For neutral impurities or defects, the energy near interface and that far away from the interface are similar (⩽0.1 eV difference) for a perfect coherent interface. The Y₂O₃|bcc Fe interface should provide effective trapping sites for hydrogen atoms in oxide dispersion strengthened (ODS) steels.