Describing plutonium from first-principles theory

A new publication in the journal Advances in Physics by three Laboratory researchers describes plutonium from first-principles theory. This is the first time a first-principles explanation for the perplexing anomalous negative thermal expansion of the delta phase of plutonium has been reported. Per Söderlind, Alex Landa, and Babak Sadigh (all PHYS) reviewed developments in the theoretical description and understanding of plutonium in terms of a metal with itinerant (band) 5f electrons.

Within this picture most facets of this anomalous material are accurately described by first-principle, parameter-free, density-functional-theory calculations. The team showed that the model explains plutonium’s phase stability, elasticity, lattice vibrations, electronic structure, alloy properties, and magnetism. The team also showed that the spin fluctuations respond to temperature in such a way that bonding increases with a resulting negative contribution to the thermal expansion that more than compensate for the normal positive expansion associated with lattice vibrations.

This work was partly funded by the Laboratory Directed Research and Development Program (11-ER-033 and 17-ERD-041).

[P. Söderlind, A. Landa, and B. Sadigh, Density-functional theory for plutonium, Advances in Physics 68 (1), 1–47 (2019), doi: 10.1080/00018732.2019.1599554.]