Soft phonons in -phase plutonium near the transitionRuqing Xu1, 2, Joe Wong3, Paul Zschack4, Hawoong Hong2 and Tai-C. Chiang1, 2
1 Department of Physics, University of Illinois at Urbana-Champaign - 1110 W. Green Street, Urbana, IL 61801, USA
2 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign - 104 S. Goodwin Avenue, Urbana, IL 61801, USA
3 Lawrence Livermore National Laboratory, University of California - P.O. Box 808, Livermore, CA 94551, USA
4 Advanced Photon Source, Argonne National Laboratory - Argonne, IL 60439, USA
received 6 December 2007; accepted in final form 18 February 2008; published April 2008
published online 26 March 2008
Plutonium and its alloys exhibit complex phase diagrams that imply anomalous lattice dynamics near phase stability boundaries. Specifically, the TA  phonon branch in Ga-stabilized -Pu at room temperature shows a pronounced soft mode at the zone boundary, which suggests a possible connection to the martensitic transformation from the fcc -phase to the monoclinic -phase at low temperatures. This work is a study of the lattice dynamics of this system by X-ray thermal diffuse scattering. The results reveal little temperature dependence of the phonon frequencies, thus indicating that kinetic phonon softening is not responsible for this phase transition.
63.20.D- - Phonon states and bands, normal modes, and phonon dispersion.
64.70.K- - Solid-solid transitions.
61.05.cf - X-ray scattering (including small-angle scattering).
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