Density functional theory investigation of the layered uranium oxides U3O8 and U2O5

Nicholas A. Brincat, Stephen C. Parker, Marco Molinari, Geoffrey C. Allen, Mark T. Storr

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Oxidation of UO2 in the nuclear fuel cycle leads to formation of the layered uranium oxides. Here we present DFT simulations of U2O5 and U3O8 using the PBE + U functional to examine their structural, electronic and mechanical properties. We build on previous simulation studies of Amm2 α-U3O8, P21/m β-U3O8 and P62m γ-U3O8 by including C222 α-U3O8, Cmcm β-U3O8 and Pnma δ-U2O5. All materials are predicted to be insulators with no preference for ferromagnetic or antiferromagnetic ordering. We predict δ-U2O5 contains exclusively U5+ ions in an even mixture of distorted octahedral and pentagonal bipyramidal coordination sites. In each U3O8 polymorph modelled we predict U5+ ions in pentagonal bipyramidal coordination and U6+ in octahedral coordination, with no U4+ present. The elastic constants of each phase have been calculated and the bulk modulus is found to be inversely proportional to the volume per uranium ion. Finally, a number of thermodynamic properties are estimated, showing general agreement with available experiments; for example α- and β-U3O8 are predicted to be stable at low temperatures but β-U3O8 and γ-U3O8 dominate at high temperature and high pressure respectively.

Original languageEnglish
Pages (from-to)2613-2622
Number of pages10
JournalDalton Transactions
Volume44
Issue number6
Early online date10 Nov 2014
DOIs
Publication statusPublished - 28 Jan 2015
Externally publishedYes

Fingerprint

Density functional theory
Ions
uranium oxide
uranium octoxide
Uranium
Nuclear fuels
Elastic constants
Polymorphism
Discrete Fourier transforms
Electronic properties
Structural properties
Thermodynamic properties
Elastic moduli
Oxidation
Mechanical properties
Temperature

Cite this

Brincat, Nicholas A. ; Parker, Stephen C. ; Molinari, Marco ; Allen, Geoffrey C. ; Storr, Mark T. / Density functional theory investigation of the layered uranium oxides U3O8 and U2O5. In: Dalton Transactions. 2015 ; Vol. 44, No. 6. pp. 2613-2622.
@article{242436c4f06049a88866f6eb2e03c2cf,
title = "Density functional theory investigation of the layered uranium oxides U3O8 and U2O5",
abstract = "Oxidation of UO2 in the nuclear fuel cycle leads to formation of the layered uranium oxides. Here we present DFT simulations of U2O5 and U3O8 using the PBE + U functional to examine their structural, electronic and mechanical properties. We build on previous simulation studies of Amm2 α-U3O8, P21/m β-U3O8 and P62m γ-U3O8 by including C222 α-U3O8, Cmcm β-U3O8 and Pnma δ-U2O5. All materials are predicted to be insulators with no preference for ferromagnetic or antiferromagnetic ordering. We predict δ-U2O5 contains exclusively U5+ ions in an even mixture of distorted octahedral and pentagonal bipyramidal coordination sites. In each U3O8 polymorph modelled we predict U5+ ions in pentagonal bipyramidal coordination and U6+ in octahedral coordination, with no U4+ present. The elastic constants of each phase have been calculated and the bulk modulus is found to be inversely proportional to the volume per uranium ion. Finally, a number of thermodynamic properties are estimated, showing general agreement with available experiments; for example α- and β-U3O8 are predicted to be stable at low temperatures but β-U3O8 and γ-U3O8 dominate at high temperature and high pressure respectively.",
author = "Brincat, {Nicholas A.} and Parker, {Stephen C.} and Marco Molinari and Allen, {Geoffrey C.} and Storr, {Mark T.}",
year = "2015",
month = "1",
day = "28",
doi = "10.1039/c4dt02493a",
language = "English",
volume = "44",
pages = "2613--2622",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "6",

}

Density functional theory investigation of the layered uranium oxides U3O8 and U2O5. / Brincat, Nicholas A.; Parker, Stephen C.; Molinari, Marco; Allen, Geoffrey C.; Storr, Mark T.

In: Dalton Transactions, Vol. 44, No. 6, 28.01.2015, p. 2613-2622.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Density functional theory investigation of the layered uranium oxides U3O8 and U2O5

AU - Brincat, Nicholas A.

AU - Parker, Stephen C.

AU - Molinari, Marco

AU - Allen, Geoffrey C.

AU - Storr, Mark T.

PY - 2015/1/28

Y1 - 2015/1/28

N2 - Oxidation of UO2 in the nuclear fuel cycle leads to formation of the layered uranium oxides. Here we present DFT simulations of U2O5 and U3O8 using the PBE + U functional to examine their structural, electronic and mechanical properties. We build on previous simulation studies of Amm2 α-U3O8, P21/m β-U3O8 and P62m γ-U3O8 by including C222 α-U3O8, Cmcm β-U3O8 and Pnma δ-U2O5. All materials are predicted to be insulators with no preference for ferromagnetic or antiferromagnetic ordering. We predict δ-U2O5 contains exclusively U5+ ions in an even mixture of distorted octahedral and pentagonal bipyramidal coordination sites. In each U3O8 polymorph modelled we predict U5+ ions in pentagonal bipyramidal coordination and U6+ in octahedral coordination, with no U4+ present. The elastic constants of each phase have been calculated and the bulk modulus is found to be inversely proportional to the volume per uranium ion. Finally, a number of thermodynamic properties are estimated, showing general agreement with available experiments; for example α- and β-U3O8 are predicted to be stable at low temperatures but β-U3O8 and γ-U3O8 dominate at high temperature and high pressure respectively.

AB - Oxidation of UO2 in the nuclear fuel cycle leads to formation of the layered uranium oxides. Here we present DFT simulations of U2O5 and U3O8 using the PBE + U functional to examine their structural, electronic and mechanical properties. We build on previous simulation studies of Amm2 α-U3O8, P21/m β-U3O8 and P62m γ-U3O8 by including C222 α-U3O8, Cmcm β-U3O8 and Pnma δ-U2O5. All materials are predicted to be insulators with no preference for ferromagnetic or antiferromagnetic ordering. We predict δ-U2O5 contains exclusively U5+ ions in an even mixture of distorted octahedral and pentagonal bipyramidal coordination sites. In each U3O8 polymorph modelled we predict U5+ ions in pentagonal bipyramidal coordination and U6+ in octahedral coordination, with no U4+ present. The elastic constants of each phase have been calculated and the bulk modulus is found to be inversely proportional to the volume per uranium ion. Finally, a number of thermodynamic properties are estimated, showing general agreement with available experiments; for example α- and β-U3O8 are predicted to be stable at low temperatures but β-U3O8 and γ-U3O8 dominate at high temperature and high pressure respectively.

UR - http://www.scopus.com/inward/record.url?scp=84922120769&partnerID=8YFLogxK

U2 - 10.1039/c4dt02493a

DO - 10.1039/c4dt02493a

M3 - Article

VL - 44

SP - 2613

EP - 2622

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 6

ER -