Schedule Nov 18, 2002
Structural Instabilities of the High-Temperature Phases in Metallic Plutonium
Sergej Savrasov, New Jersey Institute
http://physics.njit.edu/~savrasov/
To understand the microscopic mechanism underlying the structural changes in plutonium, simultaneous electronic structure and lattice dynamics calculations are needed.

Here we report these studies by a new computational method based on the dynamical mean field and the linear response theories. This method allows us to incorporate correlation effects between f-electrons, which are important for modeling arbitrary waves of atomic displacements. We compute phonon dispersion relations for the high-temperature phases and find an intrinsic instability of the bcc epsilon-Pu. By estimating the entropy associated with the phonon dynamics in delta and epsilon phases we explain the origin of the delta->epsilon transition as driven by phonon entropy.

The calculated phonon spectra provide an important insight on the vibrations of the Pu lattice.

(**In collaboration with X. Dai, G. Kotliar, A. Migliori, and E. Abrahams)

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