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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Lattice expansion by intrinsic defects in uranium by molecular dynamics simulation
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Sodalite as a vehicle to increase Re retention in waste glass simulant during vitrification
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Phase-field simulations of the impact of bimodal pore size distributions on solid-state densification
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Massively parallel simulations of hemodynamics in the primary large arteries of the human vasculature
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Transient modeling and simulation of a nonisothermal sodium–sulfur cell
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Direct comparison of microstructure-sensitive fatigue crack initiation via crystal plasticity simulations and in situ high-energy X-ray experiments
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Phase Field Simulations of Elastic Deformation-Driven Grain Growth in 2D Copper Polycrystals
In this work, a phase field grain growth model coupled with a spectral stress calculation method is used to investigate the effect of applied elastic deformation on grain growth in 2D copper polycrystals with isotropic grain boundary properties. The applied deformation accelerates the grain growth compared to a relaxed polycrystal, though the effect of the deformation decreases rapidly with time. The softest grain orientations with respect to the applied deformation grow at the expense of other orientations, though they have higher elastic energy density. Due to a rapid decrease in the elastic energy stored in the system, the GB energy eventually dominates the growth leading to a linear change in the average grain area with time. Increasing the magnitude of the applied deformation accelerates the growth, while increasing the temperature accelerates the growth but decreases the effect of the applied deformation.
Ab initio molecular dynamics simulations of low energy recoil events in ceramics
The recent progress in the use of large-scale ab initio molecular dynamics (AIMD) to investigate low energy recoil events and determine threshold displacement energies, Ed, in ceramics is reviewed. In general, Ed shows a significant dependence on recoil direction and atom. In 3C-SiC, the minimum Ed for both C and Si atoms is found along the <100> direction, with a value of 20 and 49 eV, respectively. The results demonstrate that significant charge transfer occurs during the dynamics process, and defects can enhance charge transfer to surrounding atoms, which provides important insights into the formation of charged defects. It is found that the C vacancy is a positively charged defect, whereas the Si vacancy is in its neutral state. The minimum Ed in GaN is determined to be 17 and 39 eV for N and Ga atoms, respectively, both along the direction. The average Ed for N atoms (32.4 eV) is smaller than that for Ga atoms (73.2 eV). It is of interest to note that the N defects created along different crystallographic directions have a similar configuration (a N-N dumbbell configuration), but various configurations for Ga defects are formed. In Y2Ti2O7 prochlore, the minimum Ed for Y atoms is determined to be 27 eV for a recoil along the <100> direction, 31.5 eV for Ti atoms along the <100> direction, 14.5 eV for O48f atoms along the <110> direction and 13 eV for O8b atoms along the <111> direction. The average Ed values determined are 32.7, 34.2, 14.2 and 16.1 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials at vacant 8a sites, which are generally occupied by oxygen anions, and at the bridge sites between two neighboring cations along the <010> direction are observed after low energy recoil events.
Heat transfer simulations of the UO2 particle–graphite system in TREAT fuel
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Benchmark exercise for fluid flow simulations in a liquid metal fast reactor fuel assembly
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