Structures and energetics of multiple helium atoms in a tungsten monovacancy

Song, Changhui; Hou, Jie; Kong, Xiang-Shan; Wang, Sake; Liu, C.S.

doi:10.1016/j.jnucmat.2022.153577

Cited by 7 publications

(7 citation statements)

References 40 publications

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“…We calculated the solution energy of He in the interstitial position of bcc W. As shown in Table 1 , the solution energies of He for TIS and OIS are 6.367 eV and 6.510 eV in pure W, respectively. Zhang et al calculated the solution energy of He for TIS (6.320 eV) and OIS (6.560 eV) [ 28 , 37 ], which agrees well with the results of our calculations. The equilibrium lattice of bcc W was calculated to be 3.170 Å, which is well consistent with the experimental value (3.165 Å) and previous density functional theory results (3.172 Å), indicating that our calculation method is reasonable [ 38 , 39 ].…”

Section: Resultssupporting

confidence: 89%

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

Zhang

Qiu

et al. 2022

Materials

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We systematically investigated the influence of yttrium (Y) on the evolution behavior of helium (He) in tungsten (W) by first-principles calculations. It is found that the addition of Y reduces the solution energy of He atoms in W. Interestingly, the solution energy of He decreases with decreasing distance between Y and He. The binding energies between Y and He are inversely correlated with the effective charge of He atoms, which can be attributed to the closed shell structure of He. In addition, compared with pure W, the diffusion barrier (0.033 eV) of He with Y is lower, calculated by the climbing-image nudged elastic band (CI-NEB) simulations, reflecting that the existence of Y contributes to the diffusion of He in W. The obtained results provide a theoretical direction for understanding the diffusion of He.

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Section: Resultssupporting

confidence: 89%

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

Zhang

Qiu

et al. 2022

Materials

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“…Of various concerns, the interaction of He with different irradiation defects in W-PFMs causes intriguing physical phenomena [6], which has received much attention. Density functional theory (DFT) calculations have shown that an individual He atom in perfect body-centered cubic (BCC) W prefers to occupy tetrahedral interstitial sites (TISs) rather than octahedral interstitial sites (OISs) [7]. Once monovacancies exist in BCC W, a He atom is preferably trapped by a monovacancy due to the lower charge density within the vacancy [8].…”

Section: Introductionmentioning

confidence: 99%

“…Once monovacancies exist in BCC W, a He atom is preferably trapped by a monovacancy due to the lower charge density within the vacancy [8]. As the number of He atoms increases, multiple He atoms are trapped by a single vacancy, promoting the nucleation and growth of He bubbles [7]. In cases where these processes occur near the surface region of the W-PFM, nanosized fuzzy structures may form on the surface [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Electronically Temperature-Dependent Interplay between He and Trivacancy in Tungsten Plasma-Facing Materials

Fu,

Pan

2024

Materials

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Both microvoids and helium (He) impurities are widely present in tungsten (W) plasma-facing materials (PFMs), where the interaction between microvoids and He atoms has led to the intriguing development of microvoids. In this paper, we comprehensively investigated the interaction between He atoms and trivacancy (V3), a fundamental microvoid in W-PFMs, at the level of tight-binding theory. Our study showed that He atoms can catalyze the decomposition of the original V3 or facilitate its transformation into another V3 variant. We propose that a He atom near the V3 defect induces significant changes in the distribution of d-electron charges within the W atoms lining the inner wall of the V3 defect, making the W atom nearest to this He atom cationic and the other W atoms anionic. The attractive interaction between them promotes the decomposition and deformation of V3. As electronic excitation increases, the ionization of W atoms on the V3 wall gradually intensifies, thereby enhancing the cationic characteristics of the W atoms closest to the He atom. This process also prompts other W atoms to shift from anions to cations, leading to a transition in the electrostatic interactions between them from attraction to repulsion. This transformation, driven by electronic excitation, plays a significant inhibitory role in the decomposition and deformation of V3.

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“…Typically, calculations based on DFT not only produce high-precision results but also provide electronic structures of a concerned system. Previous DFT calculations have predicted that the most stable interstitials for He atoms in the W lattice are the tetrahedral interstitial sites (TIS), and the migration energy barrier of a He atom between neighboring TIS is approximately 0.06 eV [42][43][44][45][46]. At the same time, some works also showed that He atoms could be easily trapped in a W vacancy [44,45].…”

Section: Introductionmentioning

confidence: 99%

“…More importantly, DFT calculations predicted that the sites occupied by He atoms are in the regions with lower electron density. Thus, the He atoms exhibit electrophobicity [43,46]. Although the DFT method can provide electronic structures of systems, it is difficult to treat large systems.…”

Section: Introductionmentioning

confidence: 99%

Microscopic mechanism of nucleation and growth of helium bubbles in monovacancy in tungsten: helium regulates the charged states of tungsten atoms

Wang

Pan

2023

Nucl. Fusion

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In fusion reactor, tungsten (W) has been selected as a candidate for plasma-facing materials (PFMs) due to its excellent properties. However, W-PFMs suffer from helium (He) bubbles where He atoms are produced during deuterium tritium fusion in fusion reactors. To date, there have been few contributions to uncovering the formation of He bubbles from the perspective of the microscopic electronic structure of He-mediated tungsten. In this work, we develop a tight-binding potential model for the W-He interaction to study He atom aggregation and nucleation in the electronic ground state as well as in different electronic excited states. The most important finding of this paper is that caused by the He atoms in the vacancy, some d-orbital electrons of the W atoms at the inner wall of the vacancy are transferred to the W atoms farther away from the vacancy, leading to the feature of positively charged W ions at the inner wall of the vacancy. As the number of He atoms in the vacancy increases, these W ions become more cationic. Under the repulsion between these adjacent cationic ions, the volume of vacancies increases, and more He atoms tend to gather and nucleate there. At the same time, the enhancement of the electronic excitation can also promote the abovementioned electron transfer between W atoms and further increase the vacancy volume, which increases the self-aggregation of the He atoms in the vacancy. Our results shed new light on understanding He self-aggregation in many different metal materials.

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Structures and energetics of multiple helium atoms in a tungsten monovacancy

Cited by 7 publications

References 40 publications

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

Electronically Temperature-Dependent Interplay between He and Trivacancy in Tungsten Plasma-Facing Materials

Microscopic mechanism of nucleation and growth of helium bubbles in monovacancy in tungsten: helium regulates the charged states of tungsten atoms

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