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First Principles Investigations of Plutonium Americium and their Mixtures using Dynamical Mean Field Theory Washington February 5-8 (2007). Gabriel.Kotliar.

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Presentation on theme: "First Principles Investigations of Plutonium Americium and their Mixtures using Dynamical Mean Field Theory Washington February 5-8 (2007). Gabriel.Kotliar."— Presentation transcript:

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

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4 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 (F 0 F 2 F 4 F 6) Treat localization –delocalization on the same footing. LDA+DMFT. Compute total energies from a functional of the photoemission spectra.

5 DMFT Phonons in fcc  -Pu C 11 (GPa) C 44 (GPa) C 12 (GPa) C'(GPa) Theory 34.56 33.03 26.81 3.88 Experiment 36.28 33.59 26.73 4.78 ( Dai, Savrasov, Kotliar,Ledbetter, Migliori, Abrahams, Science, 9 May 2003) (experiments from Wong et.al, Science, 22 August 2003)

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

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

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

9 core valence 4d 3/2 4d 5/2 5f 5/2 5f 7/2 Excitations from 4d core to 5f valence Electron energy loss spectroscopy (EELS) or X-ray absorption spectroscopy (XAS) Energy loss [eV] Core splitting~50eV 4d 5/2 ->5f 7/2 4d 3/2 ->5f 5/2 hv Core splitting~50eV Probe for Valence and Multiplet structure: EELS&XAS A plot of the X-ray absorption as a function of energy Branching ratio B=A 5/2 /(A 5/2 +A 3/2 ) B=B0 - 4/15 /(14-n f )

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

11 One measured quantity B, two unknowns Close to atom (IC regime) Itinerancy tends to decrease B=B0 - 4/15 /(14-n f ) [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). LDA+DMFT

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

13 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.

14 Acknowlegment References-Collaborators Electronic correlations in metallic Plutonium within dynamical mean- field picture: S. Savrasov, G. Kotliar, and E. Abrahams, Nature 410, 793 (2001).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).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).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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