Invar model for δ-phase Pu: Thermal expansion, elastic and magnetic properties

A. C. Lawson; J. A. Roberts; B. Martinez; M. Ramos; G. Kotliar; F. W. Trouw; M. R. Fitzsimmons; M. P. Hehlen; J. C. Lashley; H. Ledbetter; R. J. McQueeney; A. Migliori

doi:10.1080/14786430500155262

Invar model for δ-phase Pu: Thermal expansion, elastic and magnetic properties

A. C. Lawson, J. A. Roberts, B. Martinez, M. Ramos, G. Kotliar, F. W. Trouw, M. R. Fitzsimmons, M. P. Hehlen, J. C. Lashley, H. Ledbetter, R. J. McQueeney, A. Migliori

New High Energy Theory Center

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38 Scopus citations

Abstract

We present a statistical mechanical model for the anomalous thermodynamic properties of fcc δ-phase Pu and Pu-Ga alloys. The model is based on the addition of a two-level 'Invar-like electronic energy structure to the ordinary Debye model for the lattice, there is no assumption of magnetic character of these electronic levels. Together with the usual Debye temperature Θ and lattice Grüneisen constant γ the model includes two additional parameters, the energy spacing Δ E and an electronic Grüneisen constant Γ. Δ E is 1400K, and Γ is negative and depends strongly on the Ga content. The model accounts satisfactorily for thermal expansion, and it accounts for the anomalous decrease in the bulk modulus with temperature provided that one assumes zero elastic stiffness for the excited electronic state. This assumption is consistent with the results of the dynamic mean-field theory for Pu. We found some evidence for the hypothetical two-level structure using inelastic neutron scattering.

Original language	English (US)
Pages (from-to)	2713-2733
Number of pages	21
Journal	Philosophical Magazine
Volume	86
Issue number	17-18
DOIs	https://doi.org/10.1080/14786430500155262
State	Published - Jun 11 2006

All Science Journal Classification (ASJC) codes

Condensed Matter Physics

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10.1080/14786430500155262

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@article{df6366bdd3d045cd98d09ab3efc0dc79,

title = "Invar model for δ-phase Pu: Thermal expansion, elastic and magnetic properties",

abstract = "We present a statistical mechanical model for the anomalous thermodynamic properties of fcc δ-phase Pu and Pu-Ga alloys. The model is based on the addition of a two-level 'Invar-like electronic energy structure to the ordinary Debye model for the lattice, there is no assumption of magnetic character of these electronic levels. Together with the usual Debye temperature Θ and lattice Gr{\"u}neisen constant γ the model includes two additional parameters, the energy spacing Δ E and an electronic Gr{\"u}neisen constant Γ. Δ E is 1400K, and Γ is negative and depends strongly on the Ga content. The model accounts satisfactorily for thermal expansion, and it accounts for the anomalous decrease in the bulk modulus with temperature provided that one assumes zero elastic stiffness for the excited electronic state. This assumption is consistent with the results of the dynamic mean-field theory for Pu. We found some evidence for the hypothetical two-level structure using inelastic neutron scattering.",

author = "Lawson, {A. C.} and Roberts, {J. A.} and B. Martinez and M. Ramos and G. Kotliar and Trouw, {F. W.} and Fitzsimmons, {M. R.} and Hehlen, {M. P.} and Lashley, {J. C.} and H. Ledbetter and McQueeney, {R. J.} and A. Migliori",

note = "Funding Information: We are pleased to thank Jason Cooley, Olle Eriksson, Walt Harrison, Sig Hecker, John Joyce, Jon Lawrence, Anna Llobet-Megias, Amy Ross, Jim Smith, Per S{\"o}derlind and Melissa Sweeney for discussions, the use of figures or other essential contributions. This research is sponsored by the US Department of Energy National Nuclear Security Administration and the Office of Science. The work has benefited from the use of the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory and of the LANSCE at Los Alamos National Laboratory. IPNS is funded by the US Department of Energy, BES-Materials Science, under contract W-31-109-ENG-38, and LANSCE is funded by the US Department of Energy under contract W-7405-ENG-36.",

year = "2006",

month = jun,

day = "11",

doi = "10.1080/14786430500155262",

language = "English (US)",

volume = "86",

pages = "2713--2733",

journal = "Philosophical Magazine",

issn = "1478-6435",

publisher = "Taylor and Francis Ltd.",

number = "17-18",

}

Invar model for δ-phase Pu : Thermal expansion, elastic and magnetic properties. / Lawson, A. C.; Roberts, J. A.; Martinez, B.; Ramos, M.; Kotliar, G.; Trouw, F. W.; Fitzsimmons, M. R.; Hehlen, M. P.; Lashley, J. C.; Ledbetter, H.; McQueeney, R. J.; Migliori, A.

In: Philosophical Magazine, Vol. 86, No. 17-18, 11.06.2006, p. 2713-2733.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Invar model for δ-phase Pu

T2 - Thermal expansion, elastic and magnetic properties

AU - Lawson, A. C.

AU - Roberts, J. A.

AU - Martinez, B.

AU - Ramos, M.

AU - Kotliar, G.

AU - Trouw, F. W.

AU - Fitzsimmons, M. R.

AU - Hehlen, M. P.

AU - Lashley, J. C.

AU - Ledbetter, H.

AU - McQueeney, R. J.

AU - Migliori, A.

N1 - Funding Information: We are pleased to thank Jason Cooley, Olle Eriksson, Walt Harrison, Sig Hecker, John Joyce, Jon Lawrence, Anna Llobet-Megias, Amy Ross, Jim Smith, Per Söderlind and Melissa Sweeney for discussions, the use of figures or other essential contributions. This research is sponsored by the US Department of Energy National Nuclear Security Administration and the Office of Science. The work has benefited from the use of the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory and of the LANSCE at Los Alamos National Laboratory. IPNS is funded by the US Department of Energy, BES-Materials Science, under contract W-31-109-ENG-38, and LANSCE is funded by the US Department of Energy under contract W-7405-ENG-36.

PY - 2006/6/11

Y1 - 2006/6/11

N2 - We present a statistical mechanical model for the anomalous thermodynamic properties of fcc δ-phase Pu and Pu-Ga alloys. The model is based on the addition of a two-level 'Invar-like electronic energy structure to the ordinary Debye model for the lattice, there is no assumption of magnetic character of these electronic levels. Together with the usual Debye temperature Θ and lattice Grüneisen constant γ the model includes two additional parameters, the energy spacing Δ E and an electronic Grüneisen constant Γ. Δ E is 1400K, and Γ is negative and depends strongly on the Ga content. The model accounts satisfactorily for thermal expansion, and it accounts for the anomalous decrease in the bulk modulus with temperature provided that one assumes zero elastic stiffness for the excited electronic state. This assumption is consistent with the results of the dynamic mean-field theory for Pu. We found some evidence for the hypothetical two-level structure using inelastic neutron scattering.

AB - We present a statistical mechanical model for the anomalous thermodynamic properties of fcc δ-phase Pu and Pu-Ga alloys. The model is based on the addition of a two-level 'Invar-like electronic energy structure to the ordinary Debye model for the lattice, there is no assumption of magnetic character of these electronic levels. Together with the usual Debye temperature Θ and lattice Grüneisen constant γ the model includes two additional parameters, the energy spacing Δ E and an electronic Grüneisen constant Γ. Δ E is 1400K, and Γ is negative and depends strongly on the Ga content. The model accounts satisfactorily for thermal expansion, and it accounts for the anomalous decrease in the bulk modulus with temperature provided that one assumes zero elastic stiffness for the excited electronic state. This assumption is consistent with the results of the dynamic mean-field theory for Pu. We found some evidence for the hypothetical two-level structure using inelastic neutron scattering.

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U2 - 10.1080/14786430500155262

DO - 10.1080/14786430500155262

M3 - Article

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VL - 86

SP - 2713

EP - 2733

JO - Philosophical Magazine

JF - Philosophical Magazine

SN - 1478-6435

IS - 17-18

ER -

Invar model for δ-phase Pu: Thermal expansion, elastic and magnetic properties

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