Direct observation of the spatial distribution of primary cascade damage in tungsten

Mason, Daniel R.; Sand, Andrea E.; Yi, Xiaoou; Dudarev, S. L.

doi:10.1016/j.actamat.2017.10.031

Cited by 35 publications

(30 citation statements)

References 39 publications

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“…Details of the simulation method can be found in [20]. Similar cascade simulations have been shown to reproduce the observed experimental cluster size-frequency distribution [21,23] and spatial extent [24]. A typical relaxed cascade configuration is shown in figure 2.…”

Section: Dipole Tensor For Defects Generated By a Collision Cascadementioning

confidence: 63%

A multi-scale model for stresses, strains and swelling of reactor components under irradiation

et al. 2018

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Predicting strains, stresses and swelling in nuclear power plant components exposed to irradiation directly from the observed or computed defect and dislocation microstructure is a fundamental problem of fusion power plant design that has so far eluded a practical solution. We develop a model, free from parameters not accessible to direct evaluation or observation, that is able to provide estimates for irradiation-induced stresses and strains on a macroscopic scale, using information about the distribution of radiation defects produced by high-energy neutrons in the microstructure of materials. The model exploits the fact that elasticity equations involve no characteristic spatial scale, and hence admit a mathematical treatment that is an extension to that developed for the evaluation of elastic fields of defects on the nanoscale. In the analysis given below we use, as input, the radiation defect structure data derived from ab initio density functional calculations and large-scale molecular dynamics simulations of high-energy collision cascades. We show that strains, stresses and swelling can be evaluated using either integral equations, where the source function is given by the density of relaxation volumes of defects, or they can be computed from heterogeneous partial differential equations for the components of the stress tensor, where the density of body forces is proportional to the gradient of the density of relaxation volumes of defects. We perform a case study where strains and stresses are evaluated analytically and exactly, and develop a general finite element method implementation of the method, applicable to a broad range of predictive simulations of strains and stresses induced by irradiation in materials and components of any geometry in fission or fusion nuclear power plants.

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Section: Dipole Tensor For Defects Generated By a Collision Cascadementioning

confidence: 63%

A multi-scale model for stresses, strains and swelling of reactor components under irradiation

et al. 2018

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“…• The Derlet-Nguyen-Manh-Dudarev (DND) potential [26], has been shown to produce cascade structures that are a good match to experiment [6,12,27,28,29].…”

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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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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“…Recently the spatial distribution [11] and count per incident ion [12] of larger defect clusters has also been measured in MD simulations and in situ irradiations at cryogenic temperature, giving a characteristic length-scale of a single primary damage cascade for 150keV PKA ions in W of order one nanometre. This proves that large defects are generated sufficiently close together that the interaction between them is a significant driving force on their subsequent evolution [13,14].…”

Section: Introductionmentioning

confidence: 99%

Atomistic-object kinetic Monte Carlo simulations of irradiation damage in tungsten

Mason

Sand

Dudarev

2019

Modelling Simul. Mater. Sci. Eng.

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We describe the development of a new object kinetic Monte Carlo code where the elementary defect objects are off-lattice atomistic configurations. Atomic-level transitions are used to transform and translate objects, to split objects and to merge them together. This gradually constructs a database of atomic configurations-a set of relevant defect objects and their possible events generated on-the-fly. Elastic interactions are handled within objects with empirical potentials at short distances, and between spatially distinct objects using the dipole tensor formalism. The model is shown to evolve mobile interstitial clusters in tungsten faster than an equivalent molecular dynamics simulation, even at elevated temperatures. We apply the model to the evolution of complex defects generated using molecular dynamics simulations of primary radiation damage in tungsten. We show that we can evolve defect structures formed in cascade simulations to experimentally observable timescales of seconds while retaining atomistic detail. We conclude that the first few nanoseconds of simulation following cascade initiation would be better performed using molecular dynamics, as this will capture some of the near-temperatureindependent evolution of small highly-mobile interstitial clusters. We also conclude that, for the 20keV PKA cascades annealing simulations considered here, internal relaxations of sessile objects difficult to capture using conventional object KMC with idealised object geometries establish the conditions for long timescale evolution.

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Direct observation of the spatial distribution of primary cascade damage in tungsten

Cited by 35 publications

References 39 publications

A multi-scale model for stresses, strains and swelling of reactor components under irradiation

A multi-scale model for stresses, strains and swelling of reactor components under irradiation

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

Atomistic-object kinetic Monte Carlo simulations of irradiation damage in tungsten

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