Etude des defauts crees dans le beryllium par irradiation a basse temperature

Diffusivity of hydrogen and properties of point defects in beryllium investigated by DFT

“…In case of a divacancy would be created by neutron bombardment, it can be assumed that it dissociates into two single vacancies; this is the reason why we did not evaluate the activation barriers for the diffusion of a divacancy. This result seems to be qualitatively in accordance with some observations performed on irradiated samples by neutrons (>1 MeV at 77 K) or by electrons (>2-3 MeV at 20 K), which stated that presence of vacancy aggregate is unlikely noting however that their electron microscopy resolution was limited to about 15 Å [31].…”

“…Two different experimental values are reported in the literature for hcp beryllium. Nicoud et al [31,32] estimated E ‡ d = 0.8 eV from resistivity recovery measurements on neutron irradiated beryllium samples with incident energy of about 1 MeV and at low temperature (220-300 K). From a general point of view, the resistivity recovery cannot discriminate between different types of defects.…”

Vacancies, interstitials and gas atoms in beryllium

“…Brillouin zone sampling of the wave-functions and charge density was done using the gamma-centered Monkhorst-Pack k-point grid [5]. A detailed earlier study [4] has demonstrated that the energy cutoff of at least 450 eV and a high number of k-points (at least (12,12,12) sampling mesh) are necessary to guaranty the defect energy convergence. In some of the most resource consuming calculations we used, however, somewhat weaker restrictions (300 eV cutoff or (9,9,9) sampling mesh), which might result in a slight ($0.05 eV in the worst case) underestimation of the defect energy (cf.…”

“…The vacancy formation energy was found to be close to 0.8 eV, which is less than predicted by the earlier simulations [6][7][8][9][10], but consistent with the available experimental data. Indeed, using the known values of self-diffusion activation energies (1.6-1.7 eV [11]) and the vacancy migration energy of 0.7-0.8 eV [12], the vacancy formation energy can be estimated to fall within 0.8-1.0 eV.…”

Structure-dependent deuterium release from ion implanted beryllium: Comparison between Be(1 12¯0) and Be(poly)

“…single vacancies or self interstitials. Irradiation-induced defects have been shown to be mobile in beryllium at room temperature [11,12] and can therefore diffuse to sinks such as the surface or grain boundaries to annihilate, or face annihilation upon encountering an anti-defect. Some defects will be trapped by forming immobile impurity-defect complexes with the implanted projectile [13], preferably at the end of the collision cascade.…”