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Washington February 5-8 (2007).

This research delves into a first principles approach to studying plutonium, americium, and their mixtures with a focus on dynamical mean field theory. The study explores computational methods, relativistic effects, spin-orbit coupling, band structures, and atomic multiplet effects. The results shed light on the actinide series and the Mott transition that occurs, offering insights into the fundamental properties of these elements. The study presents new theoretical methodologies that involve collaboration between universities and experimentalists, enabling validation and progress in understanding actinides. The investigation also includes preliminary findings on compounds like PuO2 and Pu-Am mixtures, highlighting the importance of this research in addressing significant scientific problems.

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Washington February 5-8 (2007).

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  1. First Principles Investigations of Plutonium Americium and their Mixtures using Dynamical Mean Field Theory Gabriel .Kotliar Physics Department and Center for Materials Theory Rutgers University. Washington February 5-8 (2007). Funded by : DOE BES and NNSA .

  2. Outline and Conclusion • First Principles Computations of Actinides. • DMFT Results for Plutonium and Americium • Preliminary Results for compounds PuO2, Pu.5 Am.5. • Mott transition in the actinide series: important science problem. • New theoretical methodologies developed at Universities. DMFT concepts, allow close interaction with experimentalists, key validation and progress.

  3. Computational Approach to a First Principles Description of the Actinides must include • Relativistic Effects, Spin Orbit Coupling • Realistic band structure, complex structures • Atomic Multiplet effects (F0 F2 F4 F6) • Treat localization –delocalization on the same footing. • LDA+DMFT. Compute total energies from a functional of the photoemission spectra.

  4. C11 (GPa) C44 (GPa) C12 (GPa) C'(GPa) Theory 34.56 33.03 26.81 3.88 Experiment 36.28 33.59 26.73 4.78 DMFT Phonons in fcc d-Pu ( Dai, Savrasov, Kotliar,Ledbetter, Migliori, Abrahams, Science, 9 May 2003) (experiments from Wong et.al, Science, 22 August 2003)

  5. Gouder Havela Lander Volume and Spectra alpa->delta volume collapse transition F0=4,F2=6.1 F0=4.5,F2=7.15

  6. Americium f6 -> L=3, S=3, J=0 Mott Transition? "soft" phase f localized "hard" phase f bonding A.Lindbaum, S. Heathman, K. Litfin, and Y. Méresse, Phys. Rev. B 63, 214101 (2001) J.-C. Griveau, J. Rebizant, G. H. Lander, andG.KotliarPhys. Rev. Lett. 94, 097002 (2005)

  7. Am within LDA+DMFT Large multiple effects: F(0)=4.5 eV F(2)=8.0 eV F(4)=5.4 eV F(6)=4.0 eV S. Y. Savrasov, K. Haule, and G. KotliarPhys. Rev. Lett. 96, 036404 (2006)

  8. 5f7/2 valence 5f5/2 4d5/2->5f7/2 4d3/2->5f5/2 Excitations from 4d core to 5f valence hv Core splitting~50eV 4d3/2 Energy loss [eV] core 4d5/2 Probe for Valence and Multiplet structure: EELS&XAS Electron energy loss spectroscopy (EELS) or X-ray absorption spectroscopy (XAS) A plot of the X-ray absorption as a function of energy Core splitting~50eV B=B0 - 4/15<l.s>/(14-nf) Branching ratio B=A5/2/(A5/2+A3/2)

  9. From J. Shim K. Haule and G. Kotliar to appear in Nature. B=B0 - 4/15<l.s>/(14-nf) B0 = (3/5) (for d->f transitions)

  10. B=B0 - 4/15<l.s>/(14-nf) LDA+DMFT [a] G. Van der Laan et al., PRL 93, 97401 (2004). [b] G. Kalkowski et al., PRB 35, 2667 (1987) [c] K.T. Moore et al., PRB 73, 33109 (2006). One measured quantity B, two unknowns Close to atom (IC regime) Itinerancy tends to decrease <l.s>

  11. First results on Compounds, PuO2, Pu-Am mixture, 50%Pu,50%Am Lattice expands -> Kondo collapse is expected charge transfer Pu d phase stabilized by shift to mixed valence nf~5.2->nf~5.4 Hybridization decreases, but nf increases, Tk does not change significantly!

  12. Outline and Conclusion • First Principles Computations of Actinides. • DMFT Results for Plutonium and Americium • Preliminary Results for compounds PuO2, Pu.5 Am.5. • Mott transition in the actinide series: important science problem. • New theoretical methodologies developed at Universities. DMFT concepts, allow close interaction with experimentalists, key validation and progress.

  13. Acknowlegment References-Collaborators • Electronic correlations in metallic Plutonium within dynamical mean-field picture: S. Savrasov, G. Kotliar, and E. Abrahams, Nature 410, 793 (2001). • Calculated Phonon Spectra of Plutonium at High Temperatures:  X. Dai, S. Y. Savrasov, G. Kotliar, A. Migliori, H. Ledbetter, and E. Abrahams, Science 300, 953-955 (2003). • Many-Body Electronic Structure of Americium metal: Sergej Y. Savrasov, Kristjan Haule, Gabriel Kotliar,Phys. Rev. Lett. 96, 036404 (2006). • J. Shim K. Haule and G. Kotliar , Fluctuating valence in a correlated solid and the anomalous properties of delta-plutonium: to appear in Nature next month. Experimentalists: LANL: A. Migliori, (resonant ultrasound) J. Singleton (magnetotrasnport ) J. Thompson, (EELS X-Ray J. Joyce (Photoemission), J. Lashley (specific heat) Livermore: J. Wong (X Ray scattering) K. Moore J. Tobin (EELS and XAS ) M. Fluss (transport) ITU: . L. Havela J. C. Griveaux and G. Lander (transport under pressure )

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