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 .

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.

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.

DMFT Phonons in fcc DMFT Phonons in fcc -Pu-Pu

  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

( Dai, Savrasov, Kotliar,Ledbetter, Migliori, Abrahams, Science, 9 May 2003)

(experiments from Wong et.al, Science, 22 August 2003)

Volume and Spectra alpa->delta volume collapse transition

F0=4,F2=6.1

F0=4.5,F2=7.15

Gouder Havela Lander

Americium

"soft" phase

f localized

"hard" phase

f bonding

Mott Transition?

f6 -> 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.KotliarPhys. Rev. Lett. 94, 097002 (2005)

Am within LDA+DMFT

S. Y. Savrasov, K. Haule, and G. KotliarPhys. Rev. Lett. 96, 036404 (2006)

F(0)=4.5 eV F(2)=8.0 eVF(4)=5.4 eV F(6)=4.0 eV

Large multiple effects:

core

vale

nce

4d3/2

4d5/2

5f5/2

5f7/2

Exci

tati

ons

from

4d c

ore

to 5

f vale

nce

Electron energy loss spectroscopy (EELS) orX-ray absorption spectroscopy (XAS)

Energy loss [eV]

Core splitting~50eV

4d5/2->5f7/2

4d3/2->5f5/2

hv

Core

split

ting~

50

eV

Probe for Valence and Multiplet structure: EELS&XAS

A plot of the X-ray absorption as a function of energy

Branching ratio B=A5/2/(A5/2+A3/2)B=B0 - 4/15<l.s>/(14-nf)

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)

One measured quantity B, two unknownsClose to atom (IC regime)

Itinerancy tends to decrease <l.s>

B=B0 - 4/15<l.s>/(14-nf)

[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).

LD

A+

DM

FT

First results on Compounds, PuO2, Pu-Am mixture, 50%Pu,50%Am

Lattice expands -> Kondo collapse is expected

charge transferPu phase stabilized by shift tomixed valence nf~5.2->nf~5.4

Hybridization decreases, but nf increases,

Tk does not change significantly!

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.

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 )