Retention and release mechanisms of deuterium implanted into beryllium

The behavior of hydrogen in perfect wurtzite beryllium oxide is herein investigated by means of electronic structure calculations based on density functional theory. The formation energies of the following set of states of hydrogen (H, H, H, H, [Formula: see text], [Formula: see text]) are computed and their solubility is established as a function of temperature and pressure with emphasis given to conditions relevant for hydrogen-implanted materials. It is found that all magnetic states H, [Formula: see text], [Formula: see text] are unstable, while the relative stability of the non-magnetic states depends on the thermodynamic conditions: H prevails above temperatures around 900 K at standard pressure, which is the lowest temperature in experiments measuring the diffusion coefficient of hydrogen in wurtzite beryllium oxide. Under hydrogen implantation, the total concentration of hydrogen is fixed by the implantation source; it is found that molecular hydrogen prevails starting from a very low total concentration in hydrogen (as low as 10 at.fr.). Finally, the diffusion coefficient of H in beryllium oxide is calculated and the results are compared with previous experimental data.

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“…The diffusion coefficient in each direction was obtained using Fick's laws. The results are, in the c direction: (10) And in the basal planes:…”

Section: Diffusion Coefficientmentioning

confidence: 99%

Hydrogen in beryllium oxide investigated by DFT: on the relative stability of charged-state atomic versus molecular hydrogen

Hodille

Ferro

Piazza

et al. 2018

J. Phys.: Condens. Matter

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“…6) and a self-trapping term (equ. 5) are needed to reproduce the experimentally observed TPD peak forms, as was shown in [4]. The annihilation reaction uses the lowest diffusion barrier of the involved species.…”

Section: Modellingmentioning

confidence: 99%

“…To model these experimental results we use a description based on coupled reaction diffusion systems (CRDS [4]). The time evolution of the number density ρ [m ] as the vibrational frequency of the Be lattice.…”

Section: Modellingmentioning

confidence: 99%

“…3) / de-trapping (equ. 4) reactions [4], the annihilation of Frenkel pairs (equ. 6) and a self-trapping term (equ.…”

Section: Modellingmentioning

confidence: 99%

“…During the implantation phase (from t = t 0 to t i ), the temperature T is held constant at 300 K and the source terms S introduce H, MV and SIA into the sample. The source profiles are taken from static SDTrim.SP calculations [4], using deuterium as a projectile. If the implantation energy is varied, the source profiles change accordingly.…”

Section: Modellingmentioning

confidence: 99%

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

Piechoczek

Reinelt

Oberkofler

et al. 2013

Journal of Nuclear Materials

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The atomistic understanding of retention and release processes of deuterium in beryllium is reached by comparing well-defined experiments on Be(0001) and [11][12][13][14][15][16][17][18][19][20] single crystals, as well as polycrystalline Be to simulations. The experimental desorption spectra are modelled as a coupled reaction diffusion system (CRDS). The single atomistic steps are described by a set of rate equations. Activation energies for the single processes are calculated from density functional theory. (0001) is attributed to anisotropic self-interstitial diffusion influencing the availability of monovacancy traps during implantation. Additionally, desorption spectra with various temperature ramps recorded on polycrystalline Be were successfully reproduced with the CRDS code. D 2 release from polycrystalline Be occurs at lower temperatures than from the single crystals. This is attributed to fast D diffusion along grain boundaries.

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Energetics and reactivity of small beryllium deuterides

et al. 2017

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Enthalpies and free energies of reaction for small neutral and charged beryllium deuterides BeD, BeD2, and BeD3 that have been calculated are reported for a temperature range of 0 K to 1000 K. We discuss probable dissociation channels and possible ways of producing BeD by localizing the relevant transition states and by calculating corresponding rate constants. BeD and BeD+ are found to be the most stable ones among the considered compounds. BeD2 and are more likely to decompose into Be0,+ + D2 than into BeD0,+ + D. The metastable BeD3 and predominantly decompose into BeD0,+ + D2. In light of our results on the reaction energetics, we can interpret the pathways for production of BeD via BeD2 and BeD3 intermediates observed in molecular dynamics simulations.

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Retention and release mechanisms of deuterium implanted into beryllium

Cited by 31 publications

References 14 publications

Hydrogen in beryllium oxide investigated by DFT: on the relative stability of charged-state atomic versus molecular hydrogen

Hydrogen in beryllium oxide investigated by DFT: on the relative stability of charged-state atomic versus molecular hydrogen

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

Energetics and reactivity of small beryllium deuterides

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