Energetics of small helium clusters near tungsten surface by ab initio calculations

Wan, Chubin; Yu, Suye; Ju, Xin

doi:10.1016/j.jnucmat.2017.11.023

Cited by 10 publications

(4 citation statements)

References 30 publications

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“…This correlation, much like other studies of helium bubble energetics and bubble growth in tungsten [21][22][23][24][25][26][27][28][29][30] , has been useful in developing coarse-grained models of helium transport and surface morphological evolution in tungsten [31][32][33][34][35][36] . However, the correlation in Eq.…”

mentioning

confidence: 72%

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Hammond

Maroudas

Wirth

2020

Sci Rep

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We present a theoretically-motivated model of helium bubble density as a function of volume for high-pressure helium bubbles in plasma-facing tungsten. the model is a good match to the empirical correlation we published previously [Hammond et al., Acta Mater. 144, 561-578 (2018)] for small bubbles, but the current model uses no adjustable parameters. The model is likely applicable to significantly larger bubbles than the ones examined here, and its assumptions can be extended trivially to other metals and gases. We expect the model to be broadly applicable and useful in coarse-grained models of gas transport in metals.

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confidence: 72%

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Hammond

Maroudas

Wirth

2020

Sci Rep

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“…In a high fluence range of ∼3.5 ×10 26 -10 27 m −2 , D blisters on the W-Ta surface are considerably smaller in size and number than those on the W surface. [4] Theoretically, an individual H [7,8] or He [9,10] atom is energetically favorable to occupy the tetrahedral interstitial site (TIS) in bulk W. When He and H are close to each other, they form an interstitial pair and occupy relaxed tetrahedral sites in bulk W. [11] The results show that the interaction between He and defects in Ta is repulsive but is strongly attractive in W. [12] Although these two metals are similar in He production under spallation reaction, He clusters are much more difficult to form in Ta than in W.…”

mentioning

confidence: 99%

Energetics of He and H Atoms in W–Ta Alloys: First-Principle Calculations

Wan¹,

Yu²,

Ju³

2018

Chinese Phys. Lett.

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Properties of various defects of He and H atoms in W–Ta alloys are investigated based on density functional theory. The tetrahedral interstitial site is the most configured site for self-interstitial He and H in W and W–Ta alloys. Only a single He atom favors a substitutional site in the presence of a nearby vacancy. However, in the coexistence of He and H atoms in the presence of the vacancy, the single H atom favors the tetrahedral interstitial site (TIS) closest to the vacancy, and the He atom takes the vacancy center. The addition of Ta can reduce the formation energy of TIS He or H defects. The substituted Ta affects the charge density distribution in the vicinity of the He atom and decreases the valence electron density of the H atoms. A strong hybridization of the H s states and the nearest W d state s exists in W53He1H1 structure. The sequence of the He p projected DOS at the Fermi energy level is in agreement with the order of the formation energy of the He–H pair in the systems.

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“…These results clearly show a pronounced impact of the Soret effect on the transport and retention of both helium and hydrogenic species, although it is important to note that the current simulations have not included the effect of selfclustering and trapping. Self-clustering of helium in tungsten is very strong and the literature contains many references showing that the presence of surfaces can induce trap mutation at lower helium cluster sizes than in the bulk [27][28][29][30]. The thermal-gradient-driven diffusion of helium towards the plasma-facing surface may influence the selfclustering and, therefore, the retention of helium.…”

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confidence: 99%

Impact of Soret effect on hydrogen and helium retention in PFC tungsten under ELM-like conditions

et al. 2023

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In our previous work, we have demonstrated using nonequilibrium molecular-dynamics simulations that the fluxes of helium and self-interstitial atoms in the presence of a thermal gradient in tungsten are directed opposite to the heat flux, indicating that species transport is governed by a Soret effect, namely, thermal-gradient-driven diffusion, characterized by a negative heat of transport that drives species transport uphill, i.e., from the cooler to the hot regions of the tungsten sample. In this work, the findings of our thermal and species transport analysis have been implemented in our cluster-dynamics code, Xolotl, which has been used to compute temperature and species profiles over spatiotemporal scales representative of plasma-facing component (PFC) tungsten under typical reactor operating conditions, including extreme heat loads at the plasma-facing surface characteristic of plasma instabilities that induce edge localized modes (ELMs). We demonstrate that the steady-state species profiles, when properly accounting for the Soret effect, vary significantly from those where temperature-gradient-driven transport is not accounted for and discuss the implications of such a Soret effect on the response to plasma exposure of plasma-facing tungsten. Although our cluster dynamics simulations do not yet include self-clustering of helium or hydrogen blister formation, our simulation results show that the Soret effect substantially reduces helium and hydrogenic species retention inside PFC tungsten.

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Energetics of small helium clusters near tungsten surface by ab initio calculations

Cited by 10 publications

References 30 publications

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Energetics of He and H Atoms in W–Ta Alloys: First-Principle Calculations

Impact of Soret effect on hydrogen and helium retention in PFC tungsten under ELM-like conditions

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