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Title: DFT+U Study of Chemical Impurities in PuO2

Abstract

In this paper, we employ density functional theory to explore the effects of impurities in the fluorite crystal structure of PuO2. The impurities that were considered are known impurities that exist in metallic δ-phase Pu, including H, C, Fe, and Ga. These impurities were placed at various high-symmetry sites within the PuO2 structure including an octahedral interstitial site, an interstitial site with coordination to two neighboring O atoms, an O substitutional site, and a Pu substitutional site. Incorporation energies were calculated to be energetically unfavorable for all sites except the Pu substitutional site. When impurities were placed in a Pu substitutional site, complexes incorporating the impurities and O formed within the PuO2 structure. The observed defect-oxygen structures were OH, CO3, FeO5, and GaO3. The presence of these defects led to distortion of the surrounding O atoms within the structure, producing long-range disorder of O atoms. In contrast, perturbations of Pu atoms had a relatively short-range effect on the relaxed structures. These effects are demonstrated via radial distribution functions for O and Pu vacancies. Calculated electronic structure revealed hybridization of the impurity atom with the O valence states and a relative decrease in the Pu 5f states. Minor differences in bandmore » gaps were observed for the defected PuO2 structures containing H, C, and Ga. Finally, Fe-containing structures, however, were calculated to have a significantly decreased band gap, where the implementation of a Hubbard U parameter on the Fe 3d orbitals will maintain the calculated PuO2 band gap.« less

Authors:
 [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1360699
Report Number(s):
LA-UR-16-21938
Journal ID: ISSN 1932-7447
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 24; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY

Citation Formats

Hernandez, Sarah C., and Holby, Edward F. DFT+U Study of Chemical Impurities in PuO2. United States: N. p., 2016. Web. doi:10.1021/acs.jpcc.6b03469.
Hernandez, Sarah C., & Holby, Edward F. DFT+U Study of Chemical Impurities in PuO2. United States. doi:10.1021/acs.jpcc.6b03469.
Hernandez, Sarah C., and Holby, Edward F. Tue . "DFT+U Study of Chemical Impurities in PuO2". United States. doi:10.1021/acs.jpcc.6b03469. https://www.osti.gov/servlets/purl/1360699.
@article{osti_1360699,
title = {DFT+U Study of Chemical Impurities in PuO2},
author = {Hernandez, Sarah C. and Holby, Edward F.},
abstractNote = {In this paper, we employ density functional theory to explore the effects of impurities in the fluorite crystal structure of PuO2. The impurities that were considered are known impurities that exist in metallic δ-phase Pu, including H, C, Fe, and Ga. These impurities were placed at various high-symmetry sites within the PuO2 structure including an octahedral interstitial site, an interstitial site with coordination to two neighboring O atoms, an O substitutional site, and a Pu substitutional site. Incorporation energies were calculated to be energetically unfavorable for all sites except the Pu substitutional site. When impurities were placed in a Pu substitutional site, complexes incorporating the impurities and O formed within the PuO2 structure. The observed defect-oxygen structures were OH, CO3, FeO5, and GaO3. The presence of these defects led to distortion of the surrounding O atoms within the structure, producing long-range disorder of O atoms. In contrast, perturbations of Pu atoms had a relatively short-range effect on the relaxed structures. These effects are demonstrated via radial distribution functions for O and Pu vacancies. Calculated electronic structure revealed hybridization of the impurity atom with the O valence states and a relative decrease in the Pu 5f states. Minor differences in band gaps were observed for the defected PuO2 structures containing H, C, and Ga. Finally, Fe-containing structures, however, were calculated to have a significantly decreased band gap, where the implementation of a Hubbard U parameter on the Fe 3d orbitals will maintain the calculated PuO2 band gap.},
doi = {10.1021/acs.jpcc.6b03469},
journal = {Journal of Physical Chemistry. C},
number = 24,
volume = 120,
place = {United States},
year = {2016},
month = {5}
}

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