| 1. |
- Arsenlis, Athanasios, et al.
(författare)
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Enabling strain hardening simulations with dislocation dynamics
- 2007
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 15, s. 553-595
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Tidskriftsartikel (refereegranskat)abstract
- Numerical algorithms for discrete dislocation dynamics simulations areinvestigated for the purpose of enabling strain hardening simulations of singlecrystals on massively parallel computers. The algorithms investigated includethe O(N) calculation of forces, the equations of motion, time integration,adaptive mesh refinement, the treatment of dislocation core reactions and thedynamic distribution of data and work on parallel computers. A simulationintegrating all these algorithmic elements using the Parallel DislocationSimulator (ParaDiS) code is performed to understand their behaviour in concertand to evaluate the overall numerical performance of dislocation dynamicssimulations and their ability to accumulate percent of plastic strain.
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| 2. |
- Donev, Aleksandar, et al.
(författare)
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A First-Passage Kinetic Monte Carlo algorithm for complex diffusion-reaction systems
- 2010
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Ingår i: Journal of Computational Physics. - : Elsevier BV. - 0021-9991 .- 1090-2716. ; 229:9, s. 3214-3236
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Tidskriftsartikel (refereegranskat)abstract
- We develop an asynchronous event-driven First-Passage Kinetic Monte Carlo (FPKMC) algorithm for continuous time and space systems involving multiple diffusing and reacting species of spherical particles in two and three dimensions. The FPKMC algorithm presented here is based on the method introduced in Oppelstrup et al. [10] and is implemented in a robust and flexible framework. Unlike standard KMC algorithms such as the n-fold algorithm, FPKMC is most efficient at low densities where it replaces the many small hops needed for reactants to find each other with large first-passage hops sampled from exact time-dependent Green's functions, without sacrificing accuracy. We describe in detail the key components of the algorithm, including the event-loop and the sampling of first-passage probability distributions, and demonstrate the accuracy of the new method. We apply the FPKMC algorithm to the challenging problem of simulation of long-term irradiation of metals, relevant to the performance and aging of nuclear materials in current and future nuclear power plants. The problem of radiation damage spans many decades of time-scales, from picosecond spikes caused by primary cascades, to years of slow damage annealing and microstructure evolution. Our implementation of the FPKMC algorithm has been able to simulate the irradiation of a metal sample for durations that are orders of magnitude longer than any previous simulations using the standard Object KMC or more recent asynchronous algorithms. (C) 2010 Elsevier Inc. All rights reserved.
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| 3. |
- Hallberg, Håkan, et al.
(författare)
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Modeling of grain growth under fully anisotropic grain boundary energy
- 2019
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - 0965-0393. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- A level set formulation is proposed that can accurately trace the evolution of grain boundary networks in a polycrystalline aggregate while respecting grain boundary energy anisotropy. Commonly adopted simplifying assumptions related to the grain boundary energy variation with local microstructure conditions are avoided and the grain boundary energy dependence on both crystallographic misorientation and boundary plane inclination is respected. Key components in the formulation are discussed, such as an efficient and simple scheme for unequivocal identification of crystal neighbors at grain boundary junctions where an arbitrary number of crystals intersect. The method works without modifications in both two and three dimensions and is shown to provide grain boundary junction configurations that comply with classical equilibrium conditions as well as topological transforms of the grain boundary network that agree with theoretical predictions. Full grain boundary energy anisotropy is considered by adopting a parametrization of the five-parameter grain boundary energy space, as previously proposed by Bulatov et al 2014 Acta Mater. 65:161–75. Examples are provided to illustrate the relevance of the level set framework for simulations of microstructure evolution in polycrystalline solids. For example, it is clearly shown that the proposed modeling framework provides a grain boundary inclination dependence of the grain boundary energy that cannot be neglected in mesoscale simulations of grain growth.
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| 4. |
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| 5. |
- Oppelstrup, Tomas, 1977-, et al.
(författare)
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First-Passage Kinetic Monte Carlo method
- 2009
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 80:6, s. 066701-
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Tidskriftsartikel (refereegranskat)abstract
- We present a new effcient method for Monte Carlo simulations of diusion-reaction processes. First introduced by us in [Phys. Rev. Lett., 97:230602, 2006], the new algorithm skips the traditionalsmall diusion hops and propagates the diusing particles over long distances through asequence of super-hops, one particle at a time. By partitioning the simulation space into nonoverlappingprotecting domains each containing only one or two particles, the algorithm factorizesthe N-body problem of collisions among multiple Brownian particles into a set of much simplersingle-body and two-body problems. Ecient propagation of particles inside their protective domainsis enabled through the use of time-dependent Green's functions (propagators) obtained assolutions for the rst-passage statistics of random walks. The resulting Monte Carlo algorithmis event-driven and asynchronous; each Brownian particle propagates inside its own protectivedomain and on its own time clock. The algorithm reproduces the statistics of the underlyingMonte-Carlo model exactly. Extensive numerical examples demonstrate that for an importantclass of diusion-reaction models the new algorithm is effcient at low particle densities, whereother existing algorithms slow down severely.
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| 6. |
- Oppelstrup, Tomas, 1977-, et al.
(författare)
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First-Passage Monte Carlo Algorithm: Diffusion without All the Hops
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97, s. 230602-
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel Monte Carlo algorithm for N diffusing finite particles that react on collisions. Using the theory of first-passage processes and time dependent Green’s functions, we break the difficult N-body problem into independent single- and two-body propagations circumventing numerous diffusion hopsused in standard Monte Carlo simulations. The new algorithm is exact, extremely efficient, and applicablet o many important physical situations in arbitrary integer dimensions.
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