Effects of the Be₂₂W phase formation on hydrogen retention and blistering in mixed Be/W systems

We have performed first-principles density functional theory calculations to investigate the retention and migration of hydrogen in Be₂₂W, a stable low-W intermetallic compound. The solution energy of interstitial H in Be₂₂W is found to be 0.49 eV lower, while the diffusion barrier, on the other hand, is higher by 0.13 eV compared to those in pure hcp-Be. The higher solubility and lower diffusivity for H atoms make Be₂₂W a potential beneficial secondary phase in hcp-Be to impede the accumulation of H atoms, and hence better resist H blistering. We also find that in Be₂₂W, the attraction between an interstitial H and a beryllium vacancy ranges from 0.34 eV to 1.08 eV, which indicates a weaker trapping for hydrogen than in pure Be. Our calculated results suggest that small size Be₂₂W particles in hcp-Be might serve as the hydrogen trapping centers, hinder hydrogen bubble growth, and improve the resistance to irradiation void swelling, just as dispersed oxide particles in steel do.