Quantum Modeling of Hydrogen Retention in Beryllium Bulk and Vacancies

Abstract

Numerous experiments have been performed in the past few years on solid hydride deposition under berylliumseeded plasma action or on energetic hydrogen implantation into metallic beryllium. This article reports on calculations carried out using first-principles density functional theory (DFT) and discusses the results with respect to thermal desorption experiments. The structures of amorphous beryllium hydride were investigated for various H/Be ratios. They were compared to the structure of the organized BeH 2 crystal as a test for the validity of this model. The formation and reactivity of atomic vacancies were also investigated, together with atomic hydrogen trapping. Hints are proposed for hydrogen detrapping mechanisms.

Deuterium trapping and release in Be(0001), Be(11–20) and polycrystalline beryllium

“…In the case of the low fluences of the experiments with single crystals, this is a reasonable choice, because the implantation cascades as a first approximation produce Frenkel Pairs (SIA+MV), which are the first possible trap sites for hydrogen during the cascade. This is also in agreement with DFT calculations [1], where monovacancies are a possible trap site for hydrogen. Hydrogen H is here used synonymously for all hydrogen isotopes.…”

“…The trapped hydrogen inventory and depth profiles for all species are therefore calculated only based on the source terms given by SDTrim.SP. The energy barriers are taken from DFT calculations [1] and summarized in Tab. 1.…”

“…Well-defined implantation and release experiments yield characteristic desorption spectra which are interpreted by applying models based on coupled reaction diffusion rate equations. The respective activation energies for the atomistic reaction steps are determined in density functional theory (DFT) calculations [1]. The most critical property of beryllium is the strongly anisotropic diffusivity of self interstitials and hydrogen parallel and perpendicular to the Be basal planes, clearly demonstrated by the DFT results.…”

Properties of nitrogen-implanted beryllium and its interaction with energetic deuterium

“…The activation barrier for release of these atoms from their initial trapping site is therefore that for clean beryllium. The observed desorption temperature is then additionally influenced by the diffusion of D from the initial trap to the surface, as observed in [38] and [39]. …”

Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

“… We now focus on the depth-dependency characterization of the 45° geometry sample using the 325, 488 and 514 nm lasers: in figure 5 [56], [38]. However, we were not sensitive enough to detect the presence of Be-D bonds, directly.…”