Effect of Ti/Cr additive on helium diffusion and segregation in dilute vanadium alloys

The effect of Ti/Cr additive on He diffusion and segregation properties in dilute vanadium alloys is investigated using first-principles calculations. First we determined the He preference site and investigated the He-Cr/He-Ti interactions. Energetically, He prefers to segregate to Ti regions rather than Cr regions. The most stable site for interstitial He is a tetrahedral site near Ti. He-Ti interactions have a weak attraction while He-Cr interactions have a weak repulsion. Kinetically, He diffusion to Ti has a lower energy barrier; contrarily the He barrier increases towards Cr. Furthermore, we discuss the stability of Hen-Cr/Ti complexes and Hen-vacancy-Cr and Ti complexes with n = 1-8. It is found that the HenTi complexes are more stable than the HenCr complexes while the Hen-vacancy-Ti complexes are less favorable than Hen-vacancy-Cr. The findings give a reference for understanding the mechanism of He embrittlement under irradiation.