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Science 22 August 2003:
Vol. 301. no. 5636, pp. 1078 - 1080
DOI: 10.1126/science.1087179
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Reports

Phonon Dispersions of fcc {delta}-Plutonium-Gallium by Inelastic X-ray Scattering

Joe Wong,1* Michael Krisch,2 Daniel L. Farber,1 Florent Occelli,1 Adam J. Schwartz,1 Tai-C. Chiang,3 Mark Wall,1 Carl Boro,1 Ruqing Xu3

We report an experimental determination of the phonon dispersion curves in a face-centered cubic (fcc) {delta}-plutonium–0.6 weight % gallium alloy. Several unusual features, including a large elastic anisotropy, a small-shear elastic modulus C', a Kohn-like anomaly in the T1[011] branch, and a pronounced softening of the [111] transverse modes, are found. These features can be related to the phase transitions of plutonium and to strong coupling between the lattice structure and the 5f valence instabilities. Our results also provide a critical test for theoretical treatments of highly correlated 5f electron systems as exemplified by recent dynamical mean field theory calculations for {delta}-plutonium.

1 Lawrence Livermore National Laboratory, University of California, Post Office Box 808, Livermore, CA 94551, USA.
2 European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
3 Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana–Champaign, 1110 West Green Street, Urbana, IL 61801, USA.

* To whom correspondence should be addressed. E-mail: wong10{at}llnl.gov

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Science. ISSN 0036-8075 (print), 1095-9203 (online)