Temperature-dependent electronic structures, atomistic modelling and the negative thermal expansion of δ Pu

Abstract

Proximity to the localization–delocalization boundary results in strong temperature dependence of the electronic structures of strongly correlated materials. In this work, we incorporate this effect by introducing a phenomenological temperature-dependent parameterization of the modified embedded-atom method. We combine this model with molecular dynamics to simulate the diverse physical properties of the and phases of elemental plutonium. The new model improves upon earlier studies, it captures the negative thermal expansion and the strong temperature dependence of the bulk modulus in the -phase. We trace this improvement to a strong softening of phonons near the zone boundary and an increase of anharmonic effects induced by the temperature-dependent parameterization upon increasing temperature.

Keywords:

• plutonium
• negative thermal expansion
• phonon softening
• temperature-dependent electronic structures
• strong correlations
• embedded-atom method
• molecular dynamics

Acknowledgements

This work was supported by DOE BES grant number DE-FG02-99ER45761. K.B. wishes to thank the Alcatel-Lucent foundation for support. Q.Y. was supported by the DOE nuclear Energy University Program, contract No. 00088708. The authors thank Mike Baskes and Steve Valone for generously sharing their MD code and for helpful discussions.