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Title: Atomistic simulations of temperature and direction dependent threshold displacement energies in α - and γ -uranium

Abstract

We performed a systematic study of the threshold displacement energy (E d) in metallic uranium as a function of both the recoil direction and temperature using Molecular Dynamics simulations. We developed a novel orientation sampling scheme that utilizes crystallographic symmetrical geodesic grids to select directions from the orientation fundamental zone to study the directional dependency. Additionally, we studied the temperature dependency by considering both the α-uranium phase, corresponding to the ground state for temperatures ranging from 0 K to 600 K, and the γ-uranium phase, corresponding to high-temperature state for temperatures above 900 K. In this study, we compared several definitions of the threshold energy: a direction-specific threshold displacement energy (E d (θ,Φ)), an angle-averaged threshold energy ($$E_d^{ave}$$), a production probability threshold displacement energy ($$E_d^{pp}$$), and a defect count threshold displacement energy ($$E_d^{dc}$$). The direction-specific threshold displacement energies showed large angular anisotropy and variations in E d results in accordance with crystallographic considerations. Specifically, preferred defect channeling directions were observed in the [120], [1$$\bar{2}$$0], [1$$\bar{1}$$1] directions for the α-uranium, and [001], [111] directions for the γ-uranium. The production probability threshold displacement energy ($$E_d^{pp}$$) is calculated as approximately 99.2659 eV at 10 K (α-U), 103.4980 eV at 300 K (α-U), 76.0915 eV at 600 K (α-U), and 42.9929 eV at 900 K (γ-U). With exception of those calculated at 10 K, threshold displacement energies decrease with increasing temperature. Analyses of the stable defect structures showed that the most commonly observed interstitial configuration in α-uranium consists of a ( 0 1 0 ) dumbbell-like interstitial; while in γ-uranium no preferential defect configuration could be identified due to thermally-induced lattice instabilities at the elevated temperatures.

Authors:
 [1];  [2];  [3]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1485451
Report Number(s):
SAND-2018-12139J
Journal ID: ISSN 0927-0256; 669049
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Accepted Manuscript
Journal Name:
Computational Materials Science
Additional Journal Information:
Journal Volume: 157; Journal Issue: C; Journal ID: ISSN 0927-0256
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Molecular dynamic; Radiation damage; Threshold displacement energy

Citation Formats

Chen, Elton Y., Deo, Chaitanya, and Dingreville, Rémi. Atomistic simulations of temperature and direction dependent threshold displacement energies in α - and γ -uranium. United States: N. p., 2018. Web. doi:10.1016/j.commatsci.2018.10.026.
Chen, Elton Y., Deo, Chaitanya, & Dingreville, Rémi. Atomistic simulations of temperature and direction dependent threshold displacement energies in α - and γ -uranium. United States. doi:10.1016/j.commatsci.2018.10.026.
Chen, Elton Y., Deo, Chaitanya, and Dingreville, Rémi. Tue . "Atomistic simulations of temperature and direction dependent threshold displacement energies in α - and γ -uranium". United States. doi:10.1016/j.commatsci.2018.10.026. https://www.osti.gov/servlets/purl/1485451.
@article{osti_1485451,
title = {Atomistic simulations of temperature and direction dependent threshold displacement energies in α - and γ -uranium},
author = {Chen, Elton Y. and Deo, Chaitanya and Dingreville, Rémi},
abstractNote = {We performed a systematic study of the threshold displacement energy (Ed) in metallic uranium as a function of both the recoil direction and temperature using Molecular Dynamics simulations. We developed a novel orientation sampling scheme that utilizes crystallographic symmetrical geodesic grids to select directions from the orientation fundamental zone to study the directional dependency. Additionally, we studied the temperature dependency by considering both the α-uranium phase, corresponding to the ground state for temperatures ranging from 0 K to 600 K, and the γ-uranium phase, corresponding to high-temperature state for temperatures above 900 K. In this study, we compared several definitions of the threshold energy: a direction-specific threshold displacement energy (Ed (θ,Φ)), an angle-averaged threshold energy ($E_d^{ave}$), a production probability threshold displacement energy ($E_d^{pp}$), and a defect count threshold displacement energy ($E_d^{dc}$). The direction-specific threshold displacement energies showed large angular anisotropy and variations in Ed results in accordance with crystallographic considerations. Specifically, preferred defect channeling directions were observed in the [120], [1$\bar{2}$0], [1$\bar{1}$1] directions for the α-uranium, and [001], [111] directions for the γ-uranium. The production probability threshold displacement energy ($E_d^{pp}$) is calculated as approximately 99.2659 eV at 10 K (α-U), 103.4980 eV at 300 K (α-U), 76.0915 eV at 600 K (α-U), and 42.9929 eV at 900 K (γ-U). With exception of those calculated at 10 K, threshold displacement energies decrease with increasing temperature. Analyses of the stable defect structures showed that the most commonly observed interstitial configuration in α-uranium consists of a ( 0 1 0 ) dumbbell-like interstitial; while in γ-uranium no preferential defect configuration could be identified due to thermally-induced lattice instabilities at the elevated temperatures.},
doi = {10.1016/j.commatsci.2018.10.026},
journal = {Computational Materials Science},
number = C,
volume = 157,
place = {United States},
year = {2018},
month = {11}
}

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