Vacancies, interstitials and gas atoms in beryllium

Here we present the results of first-principles quantum mechanical calculations of energetic parameters of vacancies, interstitials, gas atoms (H, He) and some small point defect complexes in beryllium. It is found that the most energetically favorable position for self-interstitial is the basal octahedral one, for hydrogen atoms is the basal tetrahedral, while He atoms can be located with equal probability in basal octahedral and basal tetrahedral interstitial positions. The formation of divacancies and tri-vacancies from individual vacancies is shown to be energetically unfavorable, which implies high stability of beryllium against vacancy clustering. The preliminary estimates of diffusion pathways for H and He interstitials indicate essential differences: while hydrogen diffusion is nearly isotropic, that of He occurs preferentially in basal planes with the migration energy of only 0.1 eV.