Transport of hydrogen in metals with occupancy dependent trap energies

Schmid, K.; Toussaint, U. von; Schwarz-Selinger, T.

doi:10.1063/1.4896580

Cited by 60 publications

(54 citation statements)

References 10 publications

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“…Furthermore, the detrapping energy of the defect site has been found to be dependent on the number of hydrogen isotopes bound to the tungsten defects site. This behaviour is somehow quite general, since it has been found by DFT for vacancies [14][15][16][17][18][19], dislocations [21] and grain boundaries [21,22] in tungsten, and it has been recently included in MRE model codes by Schmid et al [23] and Hodille et al [9]. The latter implementation used in the present work, called MHIMS-Reservoir [9], can be summarized with the potential energy diagrams of figure 4.…”

Section: Mre Models: Single Trap-multi-detrapping Energymentioning

confidence: 87%

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

et al. 2017

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Fusion fuel retention (trapping) and release (desorption) from plasma-facing components are critical issues for ITER and for any future industrial demonstration reactors such as DEMO. Therefore, understanding the fundamental mechanisms behind the retention of hydrogen isotopes in first wall and divertor materials is necessary. We developed an approach that couples dedicated experimental studies with modelling at all relevant scales, from microscopic elementary steps to macroscopic observables, in order to build a reliable and predictive fusion reactor wall model. This integrated approach is applied to the ITER divertor material (tungsten), and advances in the development of the wall model are presented. An experimental dataset, including focused ion beam scanning electron microscopy, isothermal desorption, temperature programmed desorption, nuclear reaction analysis and Auger electron spectroscopy, is exploited to initialize a macroscopic rate equation wall model. This model includes all elementary steps of modelled experiments: implantation of fusion fuel, fuel diffusion in the bulk or towards the surface, fuel trapping on defects and release of trapped fuel during a thermal excursion of materials. We were able to show that a single-trap-type single-detrapping-energy model is not able to reproduce an extended parameter space study of a polycrystalline sample exhibiting a single desorption peak. It is therefore justified to use density functional theory to guide the initialization of a more complex model. This new model still contains a single type of trap, but includes the density functional theory findings that the detrapping energy varies as a function of the number of hydrogen isotopes bound to the trap. A better agreement of the model with experimental results is obtained when grain boundary defects are included, as is consistent with the polycrystalline nature of the studied sample. Refinement of this grain boundary model is discussed as well as the inclusion in the model Nuclear Fusion

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Section: Mre Models: Single Trap-multi-detrapping Energymentioning

confidence: 87%

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

et al. 2017

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“…Elastic Recoil Detection Analysis (ERDA) [21], Low Energy Ion Scattering (LEIS) and Direct Recoil Spectroscopy (DRS) [22][23][24] are also used, mostly to gain information on the surface properties. TDS can access global information related to the binding state of hydrogen in the bulk and on the surface, while ion beam analysis accesses local From the theoretical point of view, calculations and simulations have been carried out from the atomistic scales using Density Functional Theory (DFT) [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and Molecular Dynamics (MD) [39][40][41][42][43], to the macroscopic scale using Kinetic Monte Carlo (KMC) [44][45][46][47] and Macroscopic Rate Equations (MRE) [15,[48][49][50][51][52][53][54][55][56][57][58][59][60]. Combining both these approaches results in the commonly called multi-scale approach, in which KMC [44,…”

Section: Introductionmentioning

confidence: 99%

Surface coverage dependent mechanisms for the absorption and desorption of hydrogen from the W(1 1 0) and W(1 0 0) surfaces: a density functional theory investigation

et al. 2019

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“…This topic is of high relevance to model the retention and release of hydrogen from tungsten. To this end, both thermodynamic 28,29,30,31 and kinetic 32,33,34,35,36,37 models built via DFT data exist, however, thus far surface effects have not yet been included with explicit physical ground. Both models aim to simulate and interpret experimental results, mostly from TDS 38 39 , 40 , 41 , 42 , 43 , 44 .…”

Section: Introductionmentioning

confidence: 99%

Saturation of tungsten surfaces with hydrogen: A density functional theory study complemented by low energy ion scattering and direct recoil spectroscopy data

Piazza¹,

Ajmalghan²,

Ferro³

et al. 2018

Acta Materialia

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Herein, we investigate the saturation limits of hydrogen on the (110) and (100) surfaces of tungsten via Density Functional Theory (DFT) and complement our findings with experimental measurements. We present a detailed study of the various stable configurations that hydrogen can adopt upon the surfaces at coverage ratios starting below 1.0, up to the point of their experimental coverage ratios, and beyond. Our findings allow us to estimate that the saturation limit on each surface exists with one monolayer of hydrogen atoms adsorbed. In the case of (110) this corresponds to a coverage ratio of one hydrogen atom per tungsten atom, while in the case of (100) a full monolayer is present at a coverage ratio of 2.0. Preliminary Low Energy Ion Scattering (LEIS) and Direct Recoil Spectroscopy (DRS)measurements complement these results and tend to confirm the findings obtained by DFT. In particular, the preferred adsorption sites on both surfaces at any coverage, the reconstruction of the (100) surface and the saturation limits agree well. We show that depending on the coverage, hydrogen surface binding energies can be of the same magnitude as binding energies to defects like vacancies. As a consequence, surface effects should be included in models aiming to simulate retention and desorption of hydrogen from the bulk.

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Transport of hydrogen in metals with occupancy dependent trap energies

Cited by 60 publications

References 10 publications

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

Surface coverage dependent mechanisms for the absorption and desorption of hydrogen from the W(1 1 0) and W(1 0 0) surfaces: a density functional theory investigation

Saturation of tungsten surfaces with hydrogen: A density functional theory study complemented by low energy ion scattering and direct recoil spectroscopy data

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