Method to account for arbitrary strains in kinetic Monte Carlo simulations

Subramanian, Gopinath; Pérez, Danny; Uberuaga, Blas P.; Tomé, Carlos N.; Voter, Arthur F.

doi:10.1103/physrevb.87.144107

Cited by 30 publications

(29 citation statements)

References 48 publications

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“…Figure c shows a plot of the fitted rate constant k as a function of extension ratio, again, on a semilog plot. The dependence of k on the extension ratio λ (chain) is also exponential, and is consistent with a linear decrease of energy barrier with λ (chain) …”

Section: Resultssupporting

confidence: 74%

Parallel Replica Dynamics of Bead‐Spring Elastomers at Low Strain Rates

Subramanian

2018

Macro Theory & Simulations

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A new application of the recently developed superbasin‐parallel replica (ParRep) method is presented. As a demonstration of this new application, mechanical properties of elastomeric networks of Lennard‐Jones polymer chains are calculated. In this application, superbasin boundaries are placed at locations in phase space corresponding to chain breakage. It is shown that placing superbasin boundaries at this natural location satisfies the prerequisites for using superbasin‐ParRep, and for the simulations conducted, leads to a near‐ideal scaling of wall clock time with the number of replicas, thereby demonstrating the potential for a drastic extension of simulation timescales for this class of systems.

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Section: Resultssupporting

confidence: 74%

Parallel Replica Dynamics of Bead‐Spring Elastomers at Low Strain Rates

Subramanian

2018

Macro Theory & Simulations

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“…Here, these pathways and rates for uranium vacancy are calculated using DFT, which are then the input to the KMC simulations. In this work, we have employed a recently developed KMC Method 23,44 to efficiently account for arbitrary strain fields. In this method, the strain-induced changes to the migration barrier are computed using the dipole tensor approach [45][46][47][48] , as described in Sec.…”

Section: B Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

“…The Kinetic Monte Carlo (KMC) method 23,24 is used to simulate the long time evolution of uranium vacancies in UO 2 . While molecular dynamics 41 (MD) simulations have been used to simulate uranium vacancy dynamics in UO 2 42,43 , but it is limited by the accessible timescale, which is typically in the range of nanoseconds, while processes such as uranium diffusion occur on much longer time scales, even at elevated temperatures.…”

Section: B Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

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Impact of homogeneous strain on uranium vacancy diffusion in uranium dioxide

et al. 2015

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We present a detailed mechanism of, and the effect of homogeneous strains on, the migration of uranium vacancies in UO2. Vacancy migration pathways and barriers are identified using density functional theory (DFT) and the effect of uniform strain fields are accounted for using the dipole tensor approach. We report complex migration pathways and non-cubic symmetry associated with the uranium vacancy in UO2 and show that these complexities need to be carefully accounted for to predict the correct diffusion behavior of uranium vacancies. We show that under homogeneous strain fields, only the dipole tensor of the saddle with respect to the minimum is required to correctly predict the change in the energy barrier between the strained and the unstrained case. Diffusivities are computed using kinetic Monte Carlo (KMC) simulations for both neutral and fully charged state of uranium single and di-vacancies. We calculate the effect of strain on migration barriers in the temperature range 800 -1800 K for both vacancy types. Homogeneous strains as small as 2% have a considerable effect on diffusivity of both single and di-vacancies of uranium, with the effect of strain being more pronounced for single vacancies than di-vacancies. In contrast, the response of a given defect to strain is less sensitive to changes in the charge state of the defect. Further, strain leads to anisotropies in the mobility of the vacancy and the degree of anisotropy is very sensitive to the nature of the applied strain field for strain of equal magnitude. Our results suggest that the influence of strain on vacancy diffusivity will be significantly greater when single vacancies dominate the defect structure, such as sintering, while the effects will be much less substantial under irradiation conditions where di-vacancies dominate.

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“…Thirdly we need to account for the changing elastic response of the system as a whole. This is again done with the dipole tensor formalism, an approach previously exploited by Subramanian et al [59], and in a simplified form in ref [13]. If the transition takes the object from configuration (A) to (A ), then the A small box surrounding the moving atoms is defined, indicated by the hashed lines, with the atoms on the boundary fixed.…”

Section: Parameterization Of Kmc Simulationsmentioning

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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Method to account for arbitrary strains in kinetic Monte Carlo simulations

Cited by 30 publications

References 48 publications

Parallel Replica Dynamics of Bead‐Spring Elastomers at Low Strain Rates

Parallel Replica Dynamics of Bead‐Spring Elastomers at Low Strain Rates

Impact of homogeneous strain on uranium vacancy diffusion in uranium dioxide

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

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