Correlation-induced anomalies and extreme sensitivity in fcc Pu

Abstract

GGA + U density functional theory was used to study the effects of correlation on the properties of fcc Pu. The structural and elastic properties of fcc Pu are found to be highly sensitive to the Hubbard U parameter. Within an interval of 0.1 eV of the U parameter, the equilibrium lattice constants of fcc Pu can change from 0.44 to 0.47 nm. Whereas the bulk modulus can drop by a factor of 5–10, the pressure derivative, dB/dp, of the bulk modulus can rise dramatically from 5 to 16 and then drop discontinuously to a negative value before recovering to a more normal value. These observations are partially supported by existing experiments and the prediction of a negative dB/dp needs to be tested in future experiments. The 5f electron occupancy number also shows a drastic change near the transition range that clearly separates the delocalized and localized electron regions.

Keywords:

• plutonium
• density functional theory
• correlation
• Hubbard parameter
• bulk modulus
• pressure derivative
• localization
• itinerancy

Acknowledgements

The author would like to thank Jim L. Smith for his insights and many helpful discussions for all these years and J.X. Zhu and Steve Valone for their careful reading of the manuscript. The author also thanks DOE for supporting this work.