First-principles models for phase stability and radiation defects in structural materials for future fusion power-plant applications

Nguyen-Manh, D.; Lavrentiev, M. Yu.; Muzyk, M.; Dudarev, S. L.

doi:10.1007/s10853-012-6657-y

Cited by 28 publications

(20 citation statements)

References 63 publications

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“…DFT calculations of small interstitial clusters were performed for this work using the VASP ab initio simulation code, using the PAW method [45,46,47] with semi-core electrons included through the use of pseudo-potentials. It is important to emphasize that the inclusion of semi-core electrons in the valence states has a significant effect on the predicted formation energies of selfinterstitial atom (SIA) defects for all the bcc transition metals [2,48,49], and play important role on the quality of inter-atomic potential in predicting nonequilibrium properties in tungsten from cascade simulations [50]. Exchangecorrelation effects were described using the Perdew-Burke-Ernzerhof generalised gradient approximation [51].…”

Section: Small Defect Structuresmentioning

confidence: 99%

“…Just as it has been long acknowledged that the effect of radiation on materials is inherently multi-scale both in time-and spatial-dimension, so it is accepted that to model these effects requires transfer of high quality data from one model to the next [1]. The form of the data required by a coarse-grained model will vary according to its requirements, but a typical workflow in nuclear materials modelling is to find high quality structural information about individual defects from Density Functional Theory (DFT) [2,3], information about the cascade generation process from Molecular Dynamics (MD) [4,5,6], and about cascade evolution using object or atomistic Kinetic Monte Carlo (KMC) [7,8,9] or Cluster Dynamics (CD) [10,11]. This has proved successful for modelling the experimentally observed size and distribution of irradiation-induced defects formed in pure single crystalline materials [12,9].…”

Section: Introductionmentioning

confidence: 99%

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Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten

Mason

Nguyen-Manh

Marinica

et al. 2019

Journal of Applied Physics

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The low energy structures of irradiation-induced defects have been studied in detail, as these determine the available modes by which a defect can diffuse or relax. As a result, there are many studies concerning the relative energies of possible defect structures, and empirical potentials are commonly fitted to or evaluated with respect to these energies. But recently [Dudarev et. al. Nuclear Fusion 2018], we have shown how to determine the stresses, strains and swelling of reactor components under irradiation from the elastic properties of ensembles of irradiation-induced defects. These elastic properties have received comparatively little attention. Here we evaluate relaxation volumes of irradiation-induced defects in tungsten computed with empirical potentials, and compare to density functional theory results where available. Different empirical potentials give different results, but some potential-independent trends in relaxation volumes can be identified. We show that the relaxation volume of small defects can be predicted to within 10% from their point-defect count. For larger defects we provide empirical fits for the relaxation volume of as a function of size. We demonstrate that the relaxation volume associated * daniel.mason@ukaea.uk arXiv:1812.06874v1 [cond-mat.mtrl-sci] 17 Dec 2018 with a single primary-damage cascade can be estimated from the primary knock-on atom (PKA) energy. We conclude that while annihilation of vacancy-and interstitial-character defects will invariably reduce the total relaxation volume of the cascade debris, empirical potentials disagree whether coalescence of defects will reduce or increase the total relaxation volume.

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Section: Small Defect Structuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten

Mason

Nguyen-Manh

Marinica

et al. 2019

Journal of Applied Physics

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“…Extensive theoretical [31][32][33]45,[80][81][82][83][84][85] and experimental 86 Comparison between enthalpies of mixing of fcc and bcc Fe-Cr alloys calculated using DFT and CE is shown in Figs. 2(a) and 2(b).…”

Section: Fe-cr Binary Alloysmentioning

confidence: 99%

Phase stability of ternary fcc and bcc Fe-Cr-Ni alloys

et al. 2015

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The phase stability of fcc and bcc magnetic binary Fe-Cr, Fe-Ni and Cr-Ni alloys, and ternary Fe-Cr-Ni alloys is investigated using a combination of Density Functional Theory (DFT), Cluster Expansion (CE) and Magnetic Cluster Expansion (MCE) approaches. Energies, magnetic moments, and volumes of more than 500 alloy structures have been evaluated using DFT, and the predicted most stable configurations are compared with experimental observations. Deviations from the Vegard law in fcc Fe-Cr-Ni alloys, resulting from the non-linear variation of atomic magnetic moments as functions of alloy composition, are observed. Accuracy of the CE model is assessed against the DFT data, where for ternary Fe-Cr-Ni alloys the cross-validation error is found to be less than 12 meV/atom. A set of cluster interaction parameters is defined for each alloy, where it is used for predicting new ordered alloy structures. Fcc Fe2CrNi phase with Cu2NiZn-like crystal structure is predicted to be the global ground state of ternary Fe-Cr-Ni alloys, with the lowest chemical ordering temperature of 650K. DFT-based Monte Carlo (MC) simulations are applied to the investigation of order-disorder transitions in Fe-Cr-Ni alloys. Enthalpies of formation of ternary alloys predicted by MC simulations at 1600K, combined with magnetic correction derived from MCE, are in excellent agreement with experimental values measured at 1565K. The relative stability of fcc and bcc phases is assessed by comparing the free energies of alloy formation. Evaluation of the free energies involved the application of a dedicated algorithm for computing configurational entropies of the alloys. Chemical order is analyzed, as a function of temperature and composition, in terms of the Warren-Cowley Short-Range Order (SRO) parameters and effective chemical pairwise interactions. In addition to compositions close to binary intermetallic phases CrNi2, FeNi, FeNi3 and FeNi8, pronounced chemical order is found in fcc alloys near the centre of the ternary alloy composition triangle. The calculated SRO parameters compare favourably with experimental data on binary and ternary alloys. Finite temperature magnetic properties of fcc Fe-Cr-Ni alloys are investigated using an MCE Hamiltonian parameterized using a DFT database of energies and magnetic moments computed for a large number of alloy configurations. MCE simulations show that the ordered ternary Fe2CrNi alloy phase remains magnetic up to 850-900 K due to strong anti-ferromagnetic coupling between (Fe,Ni) and Cr atoms in the ternary Fe-Cr-Ni matrix.

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“…Traditional view is that any noble gas impurity should be similar to helium, since there is no chemical interaction between an inert gas atom and a solid, and hence the behaviour of noble gas atoms in a material can potentially be explained assuming that local lattice distortion increases monotonically from He to Xe. Therefore, the development of an accurate predictive model based on firstprinciples calculations for defects formed due to the accumulation of helium and other noble gases in the crystal lattice of iron, steel, a non-magnetic body-centred cubic (bcc) refractory metal or alloy, is an issue of significance for the quantification of radiation damage effects on structural integrity of fusion reactor components [3]. In this paper, we investigate small helium clusters trapped by inert-gas impurities in tungsten, and validate our theoretical study by comparison with experimental thermal desorption spectroscopy data.…”

Section: Introductionmentioning

confidence: 99%

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

Nguyen-Manh

Dudarev²

2015

Nuclear Instruments and Methods in Physics Research Section B:

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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.

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First-principles models for phase stability and radiation defects in structural materials for future fusion power-plant applications

Cited by 28 publications

References 63 publications

Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten

Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten

Phase stability of ternary fcc and bcc Fe-Cr-Ni alloys

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

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