<i>Ab initio</i>study of tungsten defects near the surface

Guerrero, C.; Gordillo, N.; Rodríguez, Iglesias; Perlado, J.M.; González, César

doi:10.1088/0965-0393/24/4/045006

Cited by 12 publications

(4 citation statements)

References 52 publications

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“…It is also important to note that the diffusion to the surface, once detrapping is activated, will be moderated by the retrapping process. The latter is because the migration energy of H and He is essentially smaller than the binding energy to the defects (being 0.5-0.9 eV for dislocations, 1.2-4.6 eV for vacancies and 1.4-5.7 eV for voids [42,43]). Several experimental works have been done to study the trapping of low-energy-implanted H isotopes in W [2,3,44,45].…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

Trapping of hydrogen and helium at dislocations in tungsten: anab initiostudy

et al. 2017

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The interaction of H or He atoms with a core of edge and screw dislocations (SDs), with Burgers vector a 0 /2 1 1 1 , is studied by means of ab initio calculations. The results show that the edge dislocations are stronger traps for H and He compared to the SDs, while the H/He affinity to both types of dislocation is significantly weaker than to a single vacancy. The lowest energy atomic configurations are rationalized on the basis of the charge density distribution and elasticity theory considerations. The results obtained contribute to the rationalization of the thermal desorption spectroscopy analysis by attributing certain peaks of the release of plasma components to the detrapping from dislocations. Complementary molecular statics (MS) calculations are performed to validate the accuracy of the recently developed W-H-He embedded atom method (EAM) and bond-order potentials. It is revealed that the EAM potential can reproduce correctly the magnitude of the interaction of H with both dislocations as compared to the ab initio results. All the potentials underestimate significantly the He-dislocation interaction and cannot describe correctly the lowest energy positions for H and He around the dislocation core. The reason for the discrepancy between ab initio and the MS results is rationalized by the analysis of the fully relaxed atomic configurations.

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Section: Comparison With Experimental Datamentioning

confidence: 99%

Trapping of hydrogen and helium at dislocations in tungsten: anab initiostudy

et al. 2017

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“…They showed that hydrogen prefers the TF position, in good agreement with other works based on DFT 20,21 . The penetration of hydrogen into the bulk via the W(100) 19,20,21 and W(110) 20,21,23,24 surfaces was also investigated by DFT, while the dissociation of molecular hydrogen was calculated via Molecular Dynamics (MD) calculations either based on DFT 25 or on model potentials 26,27 . However, in all cases, these works were conducted on a clean W surface, hence modeling a very low coverage; this is in contrast with real experimental conditions.…”

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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“…Due to its low solubility, He may precipitate as gas bubbles, enhancing irradiationinduced swelling and embrit tlement, particularly at high temperatures [3,4] and deterio rating their mechanical properties [3][4][5]. Hence, because of its importance in nuclear environments, helium impurities have been already investigated in many different metals, bcc [6][7][8][9], fcc [10,11] and hcp [12,13].…”

Section: Introductionmentioning

confidence: 99%

Volume and pressure of helium bubbles inside liquid Pb16Li. A molecular dynamics study

Fraile

Polcar

2020

Nucl. Fusion

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The behaviour of helium impurities inside metals has been well studied in the last 30 years, however, little attention has been devoted to helium atoms inside liquid metals. Here we have investigated the nucleation and coalescence processes of helium atoms inside liquid eutectic lithium–lead alloys using atomistic simulations. Several key findings regarding He bubbles inside liquid PbLi eutectic are presented. The radius versus the number of atoms has been calculated in the temperature range 600–1000 K. The trend can be fitted and likely extrapolated to larger bubbles (micrometer size). The value of thermal expansion of He bubbles is given as well and compared to the thermal expansion of bulk He. The pressure inside He bubbles has been calculated as a function of bubble size. Finally, the importance of accurate interatomic potentials for the He–metal interaction is discussed.

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Ab initiostudy of tungsten defects near the surface

Cited by 12 publications

References 52 publications

Trapping of hydrogen and helium at dislocations in tungsten: anab initiostudy

Trapping of hydrogen and helium at dislocations in tungsten: anab initiostudy

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

Volume and pressure of helium bubbles inside liquid Pb16Li. A molecular dynamics study

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