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Title: Cluster dynamics models of irradiation damage accumulation in ferritic iron. II. Effects of reaction dimensionality

Abstract

The black dot damage features which develop in iron at low temperatures exhibit significant mobility during in situ irradiation experiments via a series of discrete, intermittent, long range hops. By incorporating this mobility into cluster dynamics models, the temperature dependence of such damage structures can be explained with a surprising degree of accuracy. Such motion, however, is one dimensional in nature. This aspect of the physics has not been fully considered in prior models. This article describes one dimensional reaction kinetics in the context of cluster dynamics and applies them to the black dot problem. This allows both a more detailed description of the mechanisms by which defects execute irradiation-induced hops while allowing a full examination of the importance of kinetic assumptions in accurately assessing the development of this irradiation microstructure. Results are presented to demonstrate whether one dimensional diffusion alters the dependence of the defect population on factors such as temperature and defect hop length. Finally, the size of interstitial loops that develop is shown to depend on the extent of the reaction volumes between interstitial clusters, as well as the dimensionality of these interactions.

Authors:
;  [1]
  1. University of Tennessee, Knoxville, Tennessee 37996-2300 (United States)
Publication Date:
OSTI Identifier:
22402875
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCURACY; BUILDUP; DAMAGE; DEFECTS; DIFFUSION; FERRITIC STEELS; INTERSTITIALS; IRON; IRRADIATION; MICROSTRUCTURE; MOBILITY; PHYSICAL RADIATION EFFECTS; REACTION KINETICS; SOLID CLUSTERS; TEMPERATURE DEPENDENCE

Citation Formats

Kohnert, Aaron A., and Wirth, Brian D.. Cluster dynamics models of irradiation damage accumulation in ferritic iron. II. Effects of reaction dimensionality. United States: N. p., 2015. Web. doi:10.1063/1.4918316.
Kohnert, Aaron A., & Wirth, Brian D.. Cluster dynamics models of irradiation damage accumulation in ferritic iron. II. Effects of reaction dimensionality. United States. doi:10.1063/1.4918316.
Kohnert, Aaron A., and Wirth, Brian D.. Tue . "Cluster dynamics models of irradiation damage accumulation in ferritic iron. II. Effects of reaction dimensionality". United States. doi:10.1063/1.4918316.
@article{osti_22402875,
title = {Cluster dynamics models of irradiation damage accumulation in ferritic iron. II. Effects of reaction dimensionality},
author = {Kohnert, Aaron A. and Wirth, Brian D.},
abstractNote = {The black dot damage features which develop in iron at low temperatures exhibit significant mobility during in situ irradiation experiments via a series of discrete, intermittent, long range hops. By incorporating this mobility into cluster dynamics models, the temperature dependence of such damage structures can be explained with a surprising degree of accuracy. Such motion, however, is one dimensional in nature. This aspect of the physics has not been fully considered in prior models. This article describes one dimensional reaction kinetics in the context of cluster dynamics and applies them to the black dot problem. This allows both a more detailed description of the mechanisms by which defects execute irradiation-induced hops while allowing a full examination of the importance of kinetic assumptions in accurately assessing the development of this irradiation microstructure. Results are presented to demonstrate whether one dimensional diffusion alters the dependence of the defect population on factors such as temperature and defect hop length. Finally, the size of interstitial loops that develop is shown to depend on the extent of the reaction volumes between interstitial clusters, as well as the dimensionality of these interactions.},
doi = {10.1063/1.4918316},
journal = {Journal of Applied Physics},
number = 15,
volume = 117,
place = {United States},
year = {Tue Apr 21 00:00:00 EDT 2015},
month = {Tue Apr 21 00:00:00 EDT 2015}
}
  • Cited by 2
  • The microstructure that develops under low temperature irradiation in ferritic alloys is dominated by a high density of small (2–5 nm) defects. These defects have been widely observed to move via occasional discrete hops during in situ thin film irradiation experiments. Cluster dynamics models are used to describe the formation of these defects as an aggregation process of smaller clusters created as primary damage. Multiple assumptions regarding the mobility of these damage features are tested in the models, both with and without explicit consideration of such irradiation induced hops. Comparison with experimental data regarding the density of these defects demonstrates themore » importance of including such motions in a valid model. In particular, discrete hops inform the limited dependence of defect density on irradiation temperature observed in experiments, which the model was otherwise incapable of producing.« less
  • An improved version of a recently developed stochastic cluster dynamics (SCD) method (Marian and Bulatov, 2012) [6] is introduced as an alternative to rate theory (RT) methods for solving coupled ordinary differential equation (ODE) systems for irradiation damage simulations. SCD circumvents by design the curse of dimensionality of the variable space that renders traditional ODE-based RT approaches inefficient when handling complex defect population comprised of multiple (more than two) defect species. Several improvements introduced here enable efficient and accurate simulations of irradiated materials up to realistic (high) damage doses characteristic of next-generation nuclear systems. The first improvement is a proceduremore » for efficiently updating the defect reaction-network and event selection in the context of a dynamically expanding reaction-network. Next is a novel implementation of the τ-leaping method that speeds up SCD simulations by advancing the state of the reaction network in large time increments when appropriate. Lastly, a volume rescaling procedure is introduced to control the computational complexity of the expanding reaction-network through occasional reductions of the defect population while maintaining accurate statistics. The enhanced SCD method is then applied to model defect cluster accumulation in iron thin films subjected to triple ion-beam (Fe{sup 3+}, He{sup +} and H{sup +}) irradiations, for which standard RT or spatially-resolved kinetic Monte Carlo simulations are prohibitively expensive.« less
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  • Reduced dimensionality exact quantum and quasiclassical trajectory isotope effects are presented for the O(/sup 3/P)+H/sub 2/, D/sub 2/, and HD reactions. Two potential energy surfaces are used: the ab initio MODPOLCI and the semiempirical LEPS surfaces studied in previous papers in this series. Isotope effects are also calculated by conventional transition state theory with a Wigner tunneling correction. All the calculated results are compared to recent experimental measurements of the isotope effects. The measured values show that H atom abstraction is essentially the same from HH or HD, as is the D atom abstraction from either DD or DH. Onlymore » the reduced dimensionality quantum calculations on the MODPOLCI surface are in agreement with these results.« less