Nature of the 5f electronic structure of plutonium

Abstract

Plutonium (Pu), in which the 5 f valence electrons always wander the boundary between localized and itinerant states, exhibits quite complex crystal structures and unprecedentedly anomalous properties with respect to temperature and alloying. Understanding its chemical and physical properties, especially its 5 f electronic structure is one of the central and unsolved topics in condensed matter theory. In the present work, the electronic structures of the six allotropes of Pu (including its α, β, γ, δ, δ , and phases) at ambient pressure are studied comprehensively by means of the density functional theory in combination with the single-site dynamical mean-field theory. The band structures, total and partial density of states, valence state histograms, 5 f orbital occupancies, X-ray branching ratios, and self-energy functions are carefully studied. It is suggested that the α, β, and γ phases of Pu are typical Racah metals in which the atomic multiple effect dominates near the Fermi level. The calculated results reveal that not only the δ phase, but also all the six allotropes are archetypal mixedvalence metals with remarkable atomic eigenstate fluctuation. In consequence of that, the 5 f occupancy n 5 f is around 5.1 ∼ 5.4, which varies with respect to the atomic volume and electronic correlation strength of Pu. The 5 f electronic correlation in Pu is moderately orbital-dependent. Moreover, the 5 f electrons in the δ phase are the most correlated and localized.

Quasiparticle multiplets and 5f electronic correlation in prototypical plutonium borides

“…The calculated results are listed in table 3, giving B(PuB 6 ) > B(PuB 12 ) > B(PuB) ≈ B(PuB 2 ). That means the angular momentum coupling scheme of four compounds are assigned to intermediate coupling, which is similar to that in heavy actinides Pu [37] and Cm [43].…”

“…The pioneering advances have authenticated multiplet peaks near the Fermi level in Pu metal via observed photoemission spectroscopy and calculated quasiparticle multiplets, originating from 5f valence fluctuations and atomic multiplets [36,37]. The atomic multiplets for 5f electrons are believed to be generic in many Pu-based compounds [7,38].…”

Temperature-driven hidden 5f itinerant-localized crossover in heavy-fermion compound PuIn3

“…However, the most striking discrepancy is the narrow quasiparticle 5 f bands in the vicinity of the Fermi level. It should be pointed out that the enhanced spectral weight of 5 f states in the Fermi level at low temperature commonly exists in actinide systems 38 . It is speculated that the missing of flat 5 f bands in literature 24 is partly ascribed to the underestimation of strong correlation among the 5 f electrons without fully taking into account the many-body effects.…”

Collapse of quasiparticle multiplets and $5f$ itinerant-localized crossovers in cubic phase Pu$_{3}$Ga

“…Overall, the six stable allotropes of Pu are virtually different metals. Their 5 f electronic structures should be completely diverse [17][18][19].…”