Ab initio study on structural, magnetic phase and helium migration behaviour of FCC Fe 6.25 at.% Cr binary alloys

Ab initio calculations are implemented to investigate the structural and helium diffusion behaviour in Fe 6.25 at.% Cr binary alloys based on FCC-Fe. Our simulation results confirmed that the increase of Cr contents in the AFM phase is beneficial to strengthen the shear deformation resistance and hardness of the alloys, and also leads to greater lattice distortion. The presence of Cr atoms accelerates the migration of mono-helium atoms between tetrahedral and octahedral gaps in varying degrees, but greatly impedes the migration of helium atoms between tetrahedral interstitials or within the main lattice. The tetrahedral model is more stable than the octahedral model by 0.213 and 0.433 eV under the AFM and NM phase, respectively. The stability of the helium gap models depends on the electrostatic interaction between helium and surrounding metal atoms, and impurity atoms and magnetism do not directly affect its stability. There is a strong bonding interaction between Fe and Cr atoms, and the presence of interstitial helium atom results in net charge redistribution. This study provides valuable information for the interpretation of complex experimental phenomena.