First principles calculations of vacancy–vacancy interactions in nickel: thermal expansion effects

Megchiche, El Hocine; Mijoule, C.; Amarouche, Mohand

doi:10.1088/0953-8984/22/48/485502

Cited by 18 publications

(9 citation statements)

References 46 publications

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“…Divacancies are expected to contribute significantly to the diffusion process of interstitials and defects, as already shown in many metals (fcc-Ni [41], bcc-Fe [42] and fcc-Cu [43]) and insulator systems (Si-diamond) [44]. Also, they are well known to be at the origin of the nucleation step for loop clustering or cavity formation.…”

Section: Divacancy In Hcp-timentioning

confidence: 84%

First-principles study of diffusion and interactions of vacancies and hydrogen in hcp-titanium

Connétable

Huez

Andrieu

et al. 2011

J. Phys.: Condens. Matter

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We present a study of the stability of n-vacancies (V (n)) and hydrogens in the hexagonal close-packed titanium system computed by means of first-principles calculations. In this work, performed by using the generalized gradient approximation of density functional theory, we focused on the formation energies and the processes of migration of these defects. In the first part, the calculated formation energy of the monovacancy presents a disagreement with experimental data, as already mentioned in the literature. The activation energy is underestimated by almost 20%. The stability of compact divacancies was then studied. We show that a divacancy is more stable than a monovacancy if their migration energies are of the same order of magnitude. We also predict that the migration process in the basal plane of the divacancy is controlled by an intermediate state corresponding to a body-centered triangle (BO site). The case of the trivacancies is finally considered from an energetic point of view. In the second part, the insertion of hydrogen and the processes of its migration are discussed. We obtain a satisfactory agreement with experimental measurements. The chemical nature of the interactions between hydrogen and titanium are discussed, and we show that the H-atom presents an anionic behavior in the metal. The trapping energy of hydrogen in a monovacancy as a function of the number of hydrogen atoms is finally presented.

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Section: Divacancy In Hcp-timentioning

confidence: 84%

First-principles study of diffusion and interactions of vacancies and hydrogen in hcp-titanium

Connétable

Huez

Andrieu

et al. 2011

J. Phys.: Condens. Matter

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“…54 Results in Ni compare well to other DFT calculations. 21,22,53,96,97 Eshelby corrections were found to be negligible except for the tetra-vacancy in Ni at −0.03 eV, the hexavacancy at −0.06 −0.03 and −0.05 eV in afmD Fe, afmI Fe and Ni, respectively, and the dumbbell at −0.05, −0.08 and −0.10 eV in afmD Fe, afmI Fe and Ni, respectively. The only non-negligible effect on binding energies was for the hexavacancy, where increases of 0.05, 0.03, and 0.03 eV apply in afmD Fe, afmI Fe and Ni, respectively.…”

Section: Solute Interactions With Point Defectsmentioning

confidence: 91%

First-principles study of helium, carbon, and nitrogen in austenite, dilute austenitic iron alloys, and nickel

et al. 2013

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An extensive set of first-principles density functional theory calculations have been performed to study the behavior of He, C, and N solutes in austenite, dilute Fe-Cr-Ni austenitic alloys, and Ni in order to investigate their influence on the microstructural evolution of austenitic steel alloys under irradiation. The results show that austenite behaves much like other face-centered cubic metals and like Ni in particular. Strong similarities were also observed between austenite and ferrite. We find that interstitial He is most stable in the tetrahedral site and migrates with a low barrier energy of between 0.1 and 0.2 eV. It binds strongly into clusters as well as overcoordinated lattice defects and forms highly stable He-vacancy (V m He n ) clusters. Interstitial He clusters of sufficient size were shown to be unstable to self-interstitial emission and VHe n cluster formation. The binding of additional He and V to existing V m He n clusters increases with cluster size, leading to unbounded growth and He bubble formation. Clusters with n/m around 1.3 were found to be most stable with a dissociation energy of 2.8 eV for He and V release. Substitutional He migrates via the dissociative mechanism in a thermal vacancy population but can migrate via the vacancy mechanism in irradiated environments as a stable V 2 He complex. Both C and N are most stable octahedrally and exhibit migration energies in the range from 1.3 to 1.6 eV. Interactions between pairs of these solutes are either repulsive or negligible. A vacancy can stably bind up to two C or N atoms with binding energies per solute atom up to 0.4 eV for C and up to 0.6 eV for N. Calculations in Ni, however, show that this may not result in vacancy trapping as VC and VN complexes can migrate cooperatively with barrier energies comparable to the isolated vacancy. This should also lead to enhanced C and N mobility in irradiated materials and may result in solute segregation to defect sinks. Binding to larger vacancy clusters is most stable near their surface and increases with cluster size. A binding energy of 0.1 eV was observed for both C and N to a [001] self-interstitial dumbbell and is likely to increase with cluster size. On this basis, we would expect that, once mobile, Cottrell atmospheres of C and N will develop around dislocations and grain boundaries in austenitic steel alloys.

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“…A few studies 13,17 pointed out the significant impact of vacancy on oxygen diffusion, but a detailed mechanism was not proposed. In the present work, one nickel vacancy at the nearest neighboring position of oxygen at the octahedral site is introduced and the impact on oxygen migration is investigated.…”

Section: B Migration Of Oxygen In Nickelmentioning

confidence: 99%

“…Young et al 13 point out that oxygen atom initially at the substitutional site has to overcome a much higher migration barrier to move away from the nickel vacancy. Megchiche et al 17 also report that the binding interaction between oxygen and vacancy is significant. However, a clear understanding about effect of vacancies on oxygen migration has not yet been established and the corresponding oxygen diffusivities have not yet been accurately predicted using computational methodologies.…”

mentioning

confidence: 98%

First-principles studies on vacancy-modified interstitial diffusion mechanism of oxygen in nickel, associated with large-scale atomic simulation techniques

Fang

Shang

Wang

et al. 2014

Journal of Applied Physics

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This paper is concerned with the prediction of oxygen diffusivities in fcc nickel from first-principles calculations and large-scale atomic simulations. Considering only the interstitial octahedral to tetrahedral to octahedral minimum energy pathway for oxygen diffusion in fcc lattice, greatly underestimates the migration barrier and overestimates the diffusivities by several orders of magnitude. The results indicate that vacancies in the Ni-lattice significantly impact the migration barrier of oxygen in nickel. Incorporation of the effect of vacancies results in predicted diffusivities consistent with available experimental data. First-principles calculations show that at high temperatures the vacancy concentration is comparable to the oxygen solubility, and there is a strong binding energy and a redistribution of charge density between the oxygen atom and vacancy. Consequently, there is a strong attraction between the oxygen and vacancy in the Ni lattice, which impacts diffusion. V C 2014 AIP Publishing LLC. [http://dx.

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First principles calculations of vacancy–vacancy interactions in nickel: thermal expansion effects

Cited by 18 publications

References 46 publications

First-principles study of diffusion and interactions of vacancies and hydrogen in hcp-titanium

First-principles study of diffusion and interactions of vacancies and hydrogen in hcp-titanium

First-principles study of helium, carbon, and nitrogen in austenite, dilute austenitic iron alloys, and nickel

First-principles studies on vacancy-modified interstitial diffusion mechanism of oxygen in nickel, associated with large-scale atomic simulation techniques

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