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Washington February 5-8 (2007).

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. Outline and Conclusion.

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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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