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Title: Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study

Abstract

Plutonium (Pu) metal reacts rapidly in the presence of oxygen (O), resulting in an oxide layer that will eventually have an olive green rust appearance over time. Recent experimental work suggested that the incorporation of gallium (Ga) as an alloying impurity to stabilize the highly symmetric high temperature δ-phase lattice may also provide resistance against corrosion/oxidation of plutonium. In this paper, we modeled a 9.375 at. % Ga stabilized δ-Pu (111) surface and investigated adsorption of atomic O using all-electron density functional theory. Key findings revealed that the O bonded strongly to a Pu-rich threefold hollow fcc site with a chemisorption energy of –5.06 eV. Migration of the O atom to a Pu-rich environment was also highly sensitive to the surface chemistry of the Pu–Ga surface; when the initial on-surface O adsorption site included a bond to a nearest neighboring Ga atom, the O atom relaxed to a Ga deficient environment, thus affirming the O preference for Pu. Only one calculated final on-surface O adsorption site included a Ga-O bond, but this chemisorption energy was energetically unfavorable. Chemisorption energies for interstitial adsorption sites that included a Pu or Pu-Ga environment suggested that over-coordination of the O atom was energetically unfavorablemore » as well. Electronic structure properties of the on-surface sites, illustrated by the partial density of states, implied that the Ga 4p states indirectly but strongly influenced the Pu 6d states strongly to hybridize with the O 2p states, while also weakly influenced the Pu 5f states to hybridize with the O 2p states, even though Ga was not participating in bonding with O.« less

Authors:
 [1];  [1];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Texas at Arlington, Arlington, TX (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1224069
Alternate Identifier(s):
OSTI ID: 1250271
Report Number(s):
LA-UR-15-24290
Journal ID: ISSN 0925-8388; PII: S0925838815309427
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 653; Journal Issue: C; Journal ID: ISSN 0925-8388
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; density functional theory; plutonium-gallium; surface; oxygen; oxidation; electronic structure

Citation Formats

Hernandez, Sarah C., Wilkerson, Marianne P., and Huda, Muhammad N. Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study. United States: N. p., 2015. Web. doi:10.1016/j.jallcom.2015.08.246.
Hernandez, Sarah C., Wilkerson, Marianne P., & Huda, Muhammad N. Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study. United States. https://doi.org/10.1016/j.jallcom.2015.08.246
Hernandez, Sarah C., Wilkerson, Marianne P., and Huda, Muhammad N. Sun . "Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study". United States. https://doi.org/10.1016/j.jallcom.2015.08.246. https://www.osti.gov/servlets/purl/1224069.
@article{osti_1224069,
title = {Understanding oxygen adsorption on 9.375 at. % Ga-stabilized δ-Pu (111) surface: A DFT study},
author = {Hernandez, Sarah C. and Wilkerson, Marianne P. and Huda, Muhammad N.},
abstractNote = {Plutonium (Pu) metal reacts rapidly in the presence of oxygen (O), resulting in an oxide layer that will eventually have an olive green rust appearance over time. Recent experimental work suggested that the incorporation of gallium (Ga) as an alloying impurity to stabilize the highly symmetric high temperature δ-phase lattice may also provide resistance against corrosion/oxidation of plutonium. In this paper, we modeled a 9.375 at. % Ga stabilized δ-Pu (111) surface and investigated adsorption of atomic O using all-electron density functional theory. Key findings revealed that the O bonded strongly to a Pu-rich threefold hollow fcc site with a chemisorption energy of –5.06 eV. Migration of the O atom to a Pu-rich environment was also highly sensitive to the surface chemistry of the Pu–Ga surface; when the initial on-surface O adsorption site included a bond to a nearest neighboring Ga atom, the O atom relaxed to a Ga deficient environment, thus affirming the O preference for Pu. Only one calculated final on-surface O adsorption site included a Ga-O bond, but this chemisorption energy was energetically unfavorable. Chemisorption energies for interstitial adsorption sites that included a Pu or Pu-Ga environment suggested that over-coordination of the O atom was energetically unfavorable as well. Electronic structure properties of the on-surface sites, illustrated by the partial density of states, implied that the Ga 4p states indirectly but strongly influenced the Pu 6d states strongly to hybridize with the O 2p states, while also weakly influenced the Pu 5f states to hybridize with the O 2p states, even though Ga was not participating in bonding with O.},
doi = {10.1016/j.jallcom.2015.08.246},
url = {https://www.osti.gov/biblio/1224069}, journal = {Journal of Alloys and Compounds},
issn = {0925-8388},
number = C,
volume = 653,
place = {United States},
year = {2015},
month = {8}
}

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