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CCFE-PR(16)392016
Vacancy-mediated climb models cannot account for the fast, direct coalescence of dislocation loops seen experimentally. An alternative mechanism, self climb, allows prismatic dislocation loops to move away from their glide surface via pipe diffusion around the loop perimeter, independent of any vacancy atmosphere. Despite the known importance of se…
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CCFE-PR(16)752016
Recently, a scaling law describing the formation of defect clusters under irradiation has been established [1, 2]. A critical constraint associated with its application to phenomena occurring over a broad range of irradiation conditions is the limitation on the energy of incident particles. Incident neutrons or ions, with energies exceeding a certa…
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CCFE-PR(15)612015
A methodology to compute the distribution of interatomic distances in highly concentrated multicomponent alloys is proposed. By using the unit cell parameter and bulk modulus of the elements involved, the method accurately describes the distortion in the lattice produced by the interaction of the different atomic species. To prove this, density fun…
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CCFE-PR(15)932015
The occurrence of segregation in highly dilute alloys under irradiation is an unusual phenomenon that has so far eluded theoretical explanation. The fact that solute atoms segregate in alloys that, according to thermodynamics, exhibit full solubility, has significant practical implications, as the formation of precipitates strongly affects physical…
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CCFE-PR(15)742015
Oscillations of reflection high-energy electron diffraction (RHEED) intensities are computed using dynamical diffraction theory. The phase of the oscillations is determined using two different approaches. In the first, direct, approach, the phase is determined by identifying the time needed to reach the second oscillation minimum. In the second app…
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CCFE-PR(15)382015
Using in-situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high purity tungsten by low-dose high energy self-ion irradiation at 30K. At cryogenic temperature lattice defects have reduced mobility, so these microscope observations over a window on the initial, primary damage caused by individual coll…
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2015
Quantization of spin-wave excitations necessitates the reconsideration of the classical fluctuation-dissipation relation (FDR) used for temperature control in spin-lattice dynamics simulations of ferromagnetic metals. In this paper, Bose-Einstein statistics is used to reinterpret the Langevin dynamics of both lattice and spins, allowing quantum sta…
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CCFE-PR(15)802015
Hubbard-like Hamiltonians are widely used to describe on-site Coulomb interactions in magnetic and stronglycorrelated solids, but there is much confusion in the literature about the form these Hamiltonians should take for shells of p and d orbitals. This paper derives the most general s , p , and d orbital Hubbard-like Hamiltonians consistent with …
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CCFE-PR(15)772015
Classical phonon scattering calculations predict the drag force acting on defects and dislocations rises linearly with temperature, in direct contradiction with molecular dynamics simulations that find the drag force to be independent of temperature for nanoscale defects. Using the Mori-Zwanzig projection technique,with no recourse to elasticity or…
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CCFE-PR(15)1202015
Low-energy magnetic states and finite-temperature properties of Cr nanoclusters in bulk bcc Fe and Fe nanoclusters in bulk Cr are investigated using density functional theory (DFT) and the Heisenberg-Landau Hamiltonian based magnetic cluster expansion (MCE). We show, by means of noncollinear magnetic DFT calculations, that magnetic frustration caus…
Showing 61 - 70 of 117 UKAEA Paper Results