First-principles study on the diffusion of interstitial hydrogen in rare earth doped α-Fe

Rare-earth elements can improve the hydrogen embrittlement resistance of steel materials. In this paper, first-principles calculations were used to investigate the hydrogen trapping and diffusion mechanisms in rare-earth atoms (Y, La, Ce and Pr) doped α-Fe surface, bulk and grain boundary. The results showed that the doping of La or Ce on the surface attenuates the stability of hydrogen adsorption; in contrast, the doping of Y or Pr improves the stability. Hydrogen atom will be trapped in the void created at the subsurface due to surface rare-earth doping, making it difficult to diffuse into the bulk. Y doping increases hydrogen trapping stability at the bulk interstitial and grain boundary, while La, Ce, and Pr decrease the stability. The doping of the four rare-earth atoms significantly increased the energy barrier for hydrogen diffusion, hindering interstitial and through-crystal diffusion of hydrogen. Rare-earth atoms repel hydrogen while stabilizing H–Fe bonds through electron redistribution, enabling hydrogen trapping when bond stabilization exceeds repulsion. These findings advance rare-earth applications for enhancing hydrogen embrittlement resistance.