Trapping of He clusters by inert-gas impurities in tungsten: First-principles predictions and experimental validation

Abstract

a b s t r a c tProperties of point defects resulting from the incorporation of inert-gas atoms in bcc tungsten are investigated systematically using first-principles density functional theory (DFT) calculations. The most stable configuration for the interstitial neon, argon, krypton and xenon atoms is the tetrahedral site, similarly to what was found earlier for helium in W. The calculated formation energies for single inert-gas atoms at interstitial sites as well as at substitutional sites are much larger for Ne, Ar, Kr and Xe than for He. While the variation of the energy of insertion of inert-gas defects into interstitial configurations can be explained by a strong effect of their large atomic size, the trend exhibited by their substitutional energies is more likely related to the covalent interaction between the noble gas impurity atoms and the tungsten atoms. There is a remarkable variation exhibited by the energy of interaction between inert-gas impurities and vacancies, where a pronounced size effect is observed when going from He to Ne, Ar, Kr, Xe. The origin of this trend is explained by electronic structure calculations showing that p-orbitals play an important part in the formation of chemical bonds between a vacancy and an atom of any of the four inert-gas elements in comparison with helium, where the latter contains only 1s 2 electrons in the outer shell. The binding energies of a helium atom trapped by five different defects (He-v, Ne-v, Ar-v, Kr-v, Xe-v, where v denotes a vacancy in bcc-W) are all in excellent agreement with experimental data derived from thermal desorption spectroscopy. Attachment of He clusters to inert gas impurity atom traps in tungsten is analysed as a function of the number of successive trapping helium atoms. Variation of the Young modulus due to inert-gas impurities is analysed on the basis of data derived from DFT calculations.

Recent advances in modeling and simulation of the exposure and response of tungsten to fusion energy conditions

“…The interaction of solute atoms with inert gas atoms [136] and possible impurities in the W matrix has also been investigated [10,128] C binds very strongly with both the vacancy and the SIA, and so does H. The binding energy of an SIA with H is not negligible: 0.20 eV, and the binding energy of a vacancy with H is high: 1.43 eV [138], In a previous work, it was shown that H binds also very strongly with He clusters [139], in agreement with the experimental findings that He pre-irradiation of metals efficiently enhances the retention of hydrogen isotopes in the penetrated region. Mo does not appear to establish any interactions with vacancies, contrarily to Re whose binding energy with the vacancy is around 0.2 eV.…”

First-principles study of vacancy, interstitial, noble gas atom interstitial and vacancy clusters in bcc-W

“…Tungsten has been investigated extensively by first-principles calculations, 1-29 including the energetics and kinetics of vacancy and interstitial 2, 3,5,7,8,23,26,27 , the energetics and kinetics of Helium 6,7,[9][10][11][12] , Ar/Ne/Kr/Xe 28,29 , and Hydrogen 10,12,[15][16][17][18]20,29 , Hydrogen and vacancies 10,12,18 , and the solute−point defect interactions 19,22 . The interaction of vacancies has been investigated 4,7,8,21 , whereas the interaction of self-interstitials in W has not been reported to date.…”

First-Principles Study on Various Point Defects Formed by Hydrogen and Helium Atoms in Tungsten

“…3) Studies on tungsten receive an increasing amount of attention from scientists and engineers. [4][5][6][7][8][9][10] Tungsten is subjected to high particle fluxes in fusion reactors, not only the plasma background ions (H, D and T) but also the intrinsic impurities (He, Be and C). 11,12) Because hydrogen is one of the major plasma background ions, hydrogen (H) irradiation may result in the change of the mechanical properties of tungsten.…”

“…A number of experimental and theoretical studies were carried out to understand the interaction between the hydrogen or helium impurity and the tungsten host lattice. 1,7,8,[20][21][22][23][24][25][26][27][28][29] For example, Arkhipov et al found that hydrogen could form a blister on the tungsten surface. 20) Ye et al presented the experimental results in a divertor plasma simulator NAGDIS-II and observed the formation of hydrogen bubbles on the surface of tungsten.…”

“…[24][25][26] Guter, Nguyen, Li, and Ggrigorev et al studied the behavior of hydrogen or helium in tungsten by using the molecular dynamics simulation method. 8,[27][28][29] With the rapid development of the computer technique, computer simulation, such us first-principles calculation, [30][31][32][33][34] is now playing important role in the materials research.…”