Study of the interaction of hydrogen with grain boundaries in α-FE

The article presents results of first-principles modeling of the interaction of hydrogen with grain boundaries in α-iron. The simulation was performed in the framework of density functional theory (DFT) method of the full-potential linearised augmented-plane wave (FP LAPW) with generalised gradient approximation (GGA'96) in WIEN2k package. Three tilt grain boundaries Σ3 (111), Σ5(210) and Σ5(310) were studied. The calculated tilt grain boundaries were constructed using the coincidence site lattice model. The supercells contained 40-48 atoms, i.e. 20-24 atoms in each of the two grains. Calculated formation energies of grain boundaries are 1.46, 1.83 and 1.44 J/m2 and maximum binding energies of hydrogen to the boundaries are 0.39, 0.81 and 0.43 eV, respectively. These data are in good agreement with the results shown in other studies. The high value of trapping energy of the Σ5(210) boundary is probably due to the asymmetrical structure resulting from mutual rigid shift of the two grains, that was necessary to be introduced to provide optimum distance between Fe atoms, in contrast to the other two types of boundaries.