Investigation of helium at a Y2Ti2O7 nanocluster embedded in a BCC Fe matrix

Danielson, Thomas; Tea, Eric; Hin, Céline

doi:10.1039/c6cp05233a

Cited by 6 publications

(9 citation statements)

References 41 publications

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“…It was found that a variety of possible cluster structures with similar energetics may exist: different cage configurations obtained by SM, AS, and PD models as well as configurations with oxygen in the center found after relaxation of SM-OC, AS-OC, and PD-OC models. This contradicts the opinion in recent theoretical literature that favors the SM model [11,36,37]. Furthermore, the role of Ti was investigated by comparing results for O-v-Y and O-v-Y-Ti clusters, and the binding of oxygen monomers to the clusters was studied.…”

Section: Discussionmentioning

confidence: 75%

“…The results of the present work have consequences for the interpretation of the role of the oxide nanoclusters regarding He storage. Previous investigations [37,38] only considered cage-like SM clusters as discussed in the work of Barnard et al [11]. These authors found that the most stable He site is inside the cage of the SM cluster followed by interstitial sites at the cluster-iron interface and the tetrahedral interstitial site in bcc Fe.…”

Section: Discussionmentioning

confidence: 99%

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Investigation of structural models for O–Y and O–Y–Ti clusters in bcc Fe: a density functional theory study

Vallinayagam

Posselt²,

Faßbender³

2019

J. Phys.: Condens. Matter

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Six different structural models for atomic clusters in bcc Fe are investigated by density functional theory (DFT) calculations. Results for clusters with identical numbers of constituents (O, Y, Ti, and vacancies) are compared. It is found that the data on the stability or energetics of the relaxed clusters are comparable although their atomic configurations are often different. This contradicts the prevailing opinion in the related theoretical literature that favors the so-called structure matching model. In all studied cases, the absolute value of the total binding energy per cluster constituent becomes lower if Y is partially replaced by Ti. Therefore the driving force for the growth of O–Y clusters should be higher than that of O–Y–Ti clusters. This may be correlated with the experimental observation that the presence of Ti leads to a reduction of the size of the oxide clusters in nanostructured ferritic alloys and to a higher dispersion. Not only cage-like clusters but also clusters with oxygen in the center (cage) are investigated. In the absence of Ti, clusters with oxygen in the center attain more stability that cage-like clusters and the opposite holds for clusters with Ti. It is also shown that adding O atoms to cage-like clusters leads to structures with O in the center. In the present comprehensive DFT study only clusters with dimensions below 1 nm could be treated. This is still below or close to the limit of the experimental resolution of methods allowing for a simultaneous determination of atomic structure and composition of the clusters. These small clusters may be considered as nuclei for further structural evolution and growth during which a selection of the most favored cluster structures could occur.

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Investigation of structural models for O–Y and O–Y–Ti clusters in bcc Fe: a density functional theory study

Vallinayagam

Posselt²,

Faßbender³

2019

J. Phys.: Condens. Matter

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“…Thus, due to the oxidation that likely occurred during the hydriding step of the process, the He sequestration effects of the multilayers is diminished. However, He trapping at metal-metal oxide interfaces was shown to be an effective way to manage He inventory, such as in ODS [58][59][60]. DFT simulations showed the propensity for He to bind to Er oxide [61].…”

Section: Discussionmentioning

confidence: 99%

Helium Bubbles and Blistering in a Nanolayered Metal/Hydride Composite

et al. 2021

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Helium is insoluble in most metals and precipitates out to form nanoscale bubbles when the concentration is greater than 1 at.%, which can alter the material properties. Introducing controlled defects such as multilayer interfaces may offer some level of helium bubble management. This study investigates the effects of multilayered composites on helium behavior in ion-implanted, multilayered ErD2/Mo thin film composites. Following in-situ and ex-situ helium implantation, scanning and transmission electron microscopy showed the development of spherical helium bubbles within the matrix, but primarily at the layer interfaces. Bubble linkage and surface blistering is observed after high fluence ex-situ helium implantation. These results show the ability of metallic multilayers to alter helium bubble distributions even in the presence of a hydride layer, increasing the lifetime of materials in helium environments.

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“…Another characterization of the interaction of mHe with the cluster is possible via the incorporation, solution or formation energy [22]…”

Section: Dft Calculationsmentioning

confidence: 99%

“…For this purpose, these authors considered supercells with planar interfaces between Y 2 O 3 or Y 2 Ti 2 O 7 and bcc Fe. Sun et al [21] investigated the interaction of one or more He atoms with a cubic O-Y cluster model in bcc Fe while Danielson et al [22] considered the incorporation of a single He atom into the O-Y-Ti cluster model of Barnard et al [23]. The O-Y models of Sun et al [21] and Barnard et al [23] are based on the atomic structures of Y 2 O 3 and Y 2 Ti 2 O 7 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Interaction of O–Y and O–Y–Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms

Vallinayagam

Posselt

Faßbender

2019

J. Phys.: Condens. Matter

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Calculations based on density functional theory are performed to investigate the interaction of O–Y and O–Y–Ti clusters in bcc Fe with He atoms, vacancies (v) and self-interstitial atoms (SIA). The four different cluster structures studied in our previous work (J. Phys.: Condens. Matter 31 095701) are considered. He, v and SIA are inserted on different positions inside and in the environment of the clusters, the total energy of the corresponding supercell is minimized and the binding and incorporation energy of the three kinds of defects is determined. He in the center of a cage-like (CL) cluster is more stable than on interfacial vacant sites (IVS). In CL O–Y clusters He on an IVS is more stable than in the cluster structure with oxygen in the center, whereas there is no significant difference between the two kinds for clusters with Ti. Up to a distance of 1.5 times the iron lattice constant from the cluster center He is not stable on most of the octahedral and tetrahedral interstitial sites in the Fe matrix near the interface. Instead He is shifted towards positions closer to the cluster. Relaxation occurs to known IVS as well as to previously unknown interfacial interstitial sites. Moreover, two or three He atoms are placed on sites found to be stable after adding a single He. The corresponding binding and incorporation energies obtained after relaxation are nearly equal to the sum of the values for the interaction with a single He atom. However, placing He dimers or trimers in the environment of a vacancy may also lead to relatively low values of the incorporation energy. Also, barriers for jumps of He atoms between interfacial sites and the center of CL clusters are determined. In the CL O–Y cluster the barriers are lower than in the CL O–Y–Ti cluster, i.e. trapping and release of He is easier in the former than in the latter. v and SIA interaction with the clusters is also attractive. The binding energy of v strongly depends on the site where v is inserted while in all studied cases the SIA is annihilated at the cluster-iron interface. Present results clearly demonstrate that the oxide-based nanoclusters are strong traps for irradiation induced defects which is in agreement with experimental findings.

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Investigation of helium at a Y₂Ti₂O₇ nanocluster embedded in a BCC Fe matrix

Cited by 6 publications

References 41 publications

Investigation of structural models for O–Y and O–Y–Ti clusters in bcc Fe: a density functional theory study

Investigation of structural models for O–Y and O–Y–Ti clusters in bcc Fe: a density functional theory study

Helium Bubbles and Blistering in a Nanolayered Metal/Hydride Composite

Interaction of O–Y and O–Y–Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms

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