Interaction between vacancies and interstitial solutes (C, N, and O) in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>α</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Fe</mml:mi></mml:math>: From electronic structure to thermodynamics

Barouh, Caroline; Schuler, Thomas M.; Fu, Chu‐Chun; Nastar, Maylise

doi:10.1103/physrevb.90.054112

Cited by 93 publications

(72 citation statements)

References 59 publications

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“…However a recent theoretical study based on density functional theory (DFT) calculations leads to a very good agreement with the experimental self-diffusion coefficient in α-Fe [11]. A semiphenomenological model is used to account for magnetic disordering effects using 3 parameters: the reduced magnetization (experimental value [12]), G f ðVÞ ¼ 2.13 eV at T ¼ 0 K (DFT calculation, in agreement with previous results within AE0.1 eV [13][14][15][16][17][18]) and G f ðVÞ ¼ 1.98 eV for fully magnetically disordered α-Fe. These G f ðVÞ values are well above most experimental results but the fact that they allow a correct prediction of the self-diffusion coefficient [which is proportional to G f ðVÞ] makes them reliable, along with the simple magnetic model.…”

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confidence: 63%

“…[17] and references therein). Therefore, there are vacancy-solute clusters in the solid solution, and as the solutes are located in an off-centered position rather than inside the vacancy [17], muons and/or positrons are sensitive to the free space existing in these clusters [24] (cf., Fig. 1).…”

mentioning

confidence: 97%

“…Thus the effective vacancy formation free enthalpy in the solid solution containing impurities ðG f ðVÞ jFe-CNO Þ might be much lower than in pure α-Fe ðG f ðVÞ jFe Þ, the theoretical DFT value. V-X binding energies are quite high in α-Fe [17,[30][31][32], and could be able to balance the low solute concentrations.…”

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Equilibrium Vacancy Concentration Driven by Undetectable Impurities

et al. 2015

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By means of ab initio calculations combined to statistical mechanics, we provide new evidence that an experimentally undetectable tiny amount of impurities can be responsible for drastic changes in vacancy concentrations ([V]), inducing large deviations from an Arrhenius law even at low temperature. It is the case of O and N in α-Fe. The present finding is fully compatible with existing experiments, and changes the previous common vision that C has the dominant effect. This study provides a route for bridging the longstanding theoretical-experimental gap on the prediction of [V] in metals.

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Equilibrium Vacancy Concentration Driven by Undetectable Impurities

et al. 2015

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“…They have demonstrated the trapping of vacancy in Carbon Vacancy complexes and the non-localization of C atoms in the center of the vacancy. This attractive interaction and localization has been confirmed by ab initio calculations [7]. It has also to be underlined that positrons can be trapped in precipitates if its affinity for the material of precipitate is higher than the one of the matrix.…”

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confidence: 69%

Positron Annihilation Spectroscopy to Characterize Irradiation Induced Vacancy Type Defects in Materials for Nuclear Fission and Fusion

Barthe

2016

EPJ Web of Conferences

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In nuclear reactors, materials are submitted to irradiations and modification of their macroscopic properties such as swelling or hardening is observed… It is of first importance to understand the origin of these evolutions and how damage at the atomic scale such as vacancy and interstitials type defects can interact with each other or with solutes and impurities to make the microstructure evolved. So the properties of defects have to be determined.Positron annihilation spectroscopy (PAS) is a well-established technique to characterize materials [1]. Due to its positive charge, positron is sensitive to the local variations of the Coulomb potential in solids. As the anti-particle of the electron, both particles can annihilate leading to the emission of gamma rays with energy depending on the momentum of the electron positron annihilated pair. The detection of these gamma rays arises original information on the defects because positron can be trapped and annihilate in localized state such as vacancies. Two different and complementary annihilation characteristics can be measured. Firstly Positron Annihilation Lifetime Spectrometer (PALS) allows to measure the positron lifetime which depends on the local electron density at the annihilation site. The second characteristic is the momentum distribution of the electron positron annihilated pairs and is obtained by measuring the energy spectrum of the gamma annihilation rays using a Doppler Broadening Spectrometer (DBS). Both characteristics give the signature of the defects and allow determining some of their properties such as their nature, concentration, chemical environment... By using slow positron accelerators which produce monokinetic positrons beams with energy varying from 0.1 to 30 keV it is possible to study the depth profile of defects in thin layers from 0.1 to about 5 µm depending on the density of materials with a resolution of the order of 0.1xdepth. 22Na source based beams [2] or user facilities taking advantages of high positrons flux available around nuclear reactor (FRMII, Garching [3]) or LINAC( as in AIST in Japan [4]) are now available to study defects in materials. PAS has numerous advantages among them, it is non-destructive and can be used for conducting as well as insulating materials crystalline or amorphous. This technique is especially useful to probe vacancy defects in metals for which it is one of the only direct characterization. The annihilation characteristics can be predicted by first principle calculations and these data when available can help to identify defects. Sensitive to the single vacancy, PAS can allow to determine the size of the vacancy clusters up to a maximum of 1 nm approximately in the concentration range from 10 15 to a few 10 18 cm -3 .In nuclear science this technique is very powerful to characterize not only damage induced by irradiation but also to determine some fundamental properties of defects that are required for modeling of the microstructural evolution of materials such as formation, migration, agglomeratio...

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“…It should be mentioned that the majority of the literature data was obtained using VASP, except those of Refs. [50,52,56,66] (SIESTA code), [51] (CASTEP code), as well as those of Ref. [56] marked by the superscript "c" (PWSCF code).…”

Section: Defect Clusters In the Ground Statementioning

confidence: 99%