Oxygen induced transformations of the δ-Pu(111) surface

Taylor, Christopher D.

doi:10.1016/j.susc.2013.08.016

Cited by 10 publications

(8 citation statements)

References 88 publications

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“…This implies that the bridge-to-fcc site adsorbate configuration is achieved at the expense of introducing local structural distortions on the surface Pu atoms. Such oxygen induced distortions have been seen theoretically from the recent work of Taylor [11], but Taylor's results correspond to high adsorbate coverage (1 ML compared to 0.125 ML in this work). Nevertheless, in order to see amorphous growth of the oxide, higher coverage of O on a larger surface area slab together with molecular dynamics simulations would be required.…”

Section: Adsorption Energies and Geometriessupporting

confidence: 71%

“…Also, hybridization of Pu 6d and O 2p orbitals with some mixture of Pu 5f states are noted [7][8][9][10]. In addition, Taylor [11] concluded that initial oxidation coverage is a local environmental phenomenon, but at 1.0 monolayer (ML) coverage of oxygen, significant reconstruction of the surface (up to three atomic layers) of a PuO 2 -like structure on the topmost surface was observed. The O atoms were fourfold coordinated with Pu atoms that had been ''lifted'' out of the plane of the surface.…”

Section: Introductionmentioning

confidence: 97%

“…Previous DFT surface studies of oxygen adsorption on the d-Pu (1 1 1) surface have given initial insight into the electronic effects [7][8][9][10], and more recently the possible reconstruction of the surface [11]. To briefly summarize some key findings, molecular oxygen does dissociate as it approaches the Pu surface [7], and when the oxygen adatom approaches the surface, it binds to the surface with a threefold coordination (preferably the hollow hexagonal-closed-pack site) with adsorption energy of $8 eV.…”

Section: Introductionmentioning

confidence: 99%

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Atomic oxygen adsorption on 3.125 at.% Ga stabilized δ-Pu (1 1 1) surface

Hernandez

Venhaus

Huda

2015

Journal of Alloys and Compounds

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a b s t r a c tAll-electron density functional theory was used to investigate atomic oxygen adsorption on a gallium stabilized d-plutonium (1 1 1) surface. High symmetry on-surface and interstitial adsorption sites, along with local environment (as determined by the absence or presence of gallium) were explored. The calculations comprised full structural relaxations. Spin-orbit-coupling was also taken into account to assess the complexity of absorbate-substrate interactions. We observed that O adsorbate prefers to bind strongly to a gallium deficient environment, with the most stable site being the threefold hollow fcc site and associated chemisorption energy of À5.06 eV. The binding energies were least favored when gallium is a nearest neighbor to the O adsorbate, suggesting that the presence of gallium in a plutonium matrix tends to slow down the oxide layer growth. Although the oxygen coordination is the highest in the interstitial sites, the adsorption energy is less favored compared to on-surface adsorption, implying that the diffusion of oxygen from the surface layer into the subsurface layers is an activated process. The adsorption process induced non-trivial deformations of the surface. Additionally, some delocalization of the plutonium 5f and 6d partial electron density of states (PDOS) at the Fermi energy was observed. Further analysis in the PDOS indicated that gallium tends to suppress hybridization between the plutonium 5f and oxygen 2p orbitals, while the 6d orbitals hybridized with oxygen 2p orbitals.Published by Elsevier B.V.

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Section: Adsorption Energies and Geometriessupporting

confidence: 71%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Atomic oxygen adsorption on 3.125 at.% Ga stabilized δ-Pu (1 1 1) surface

Hernandez

Venhaus

Huda

2015

Journal of Alloys and Compounds

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“…Observation of slight mixture of hybridization with the Pu 5f states was also noted. Under significant coverage of O, slight reconstruction of the δ-Pu surface to an α-like surface was observed [9]. The phase transformation of Ga-stabilized δ-phase (≤ 2.5 at.…”

Section: Introductionmentioning

confidence: 98%

“…Past theoretical works have investigated oxygen (O) adsorption on δ-Pu (111) surface without the presence of impurities [5][6][7][8][9]. Their conclusions showed that the O adatom preferred threefold coordination and that the Pu 6d and O 2p hybridized [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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

Hernandez

Wilkerson

Huda

2015

Journal of Alloys and Compounds

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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 model 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 onsurface 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 is 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 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 when Ga was not participating in bonding with O.

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