Density-functional theory for plutonium

Söderlind, Per; Landa, A.; Sadigh, Babak

doi:10.1080/00018732.2019.1599554

Cited by 54 publications

(79 citation statements)

References 124 publications

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“…Here mono., ortho., tetra., fcc, and bcc are abbreviations of monoclinic, orthorhombic, tetragonal, face-centered cubic, and body-centered cubic, respectively. The non-equivalent sites in the low-symmetry α-Pu, β-Pu, and γ-Pu phases are depicted using Roman numerals (I ∼ VIII) 10-12 . tional DFT methods) or considering them in the calculations explicitly (beyond DFT or DFT + X methods) 33 .…”

Section: Brief Review Of Previous Resultsmentioning

confidence: 99%

Nature of the 5f electronic structure of plutonium

2020

Phys. Rev. B

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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.

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Section: Brief Review Of Previous Resultsmentioning

confidence: 99%

Nature of the 5f electronic structure of plutonium

2020

Phys. Rev. B

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“…The approach of choice was self-consistent density functional theory (DFT) with relativistic calculations including SOC. Even though including SOC in a DFT framework may pose some accuracy issues due to the treatment of the actinide-series 6p states [18,19], band structure calculations exhibit expected results such as small band gap openings and mixing of electronic states that remove degeneracies. DFT-based calculations were performed within the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) functional for the exchange correlation, and the projectoraugmented-wave method as implemented in VASP [20][21][22].…”

Section: Methodsmentioning

confidence: 99%

“…5f electrons, although spatially confined as well, are easier to remove from the atom in the lighter actinides, and become increasingly localized in energy and space for heavier actinides [17]. Transuranic elements such as Np exhibit flat, non-dispersive electronic states with high density of states in the vicinity of the Fermi energy dominated by 5f-states, which leads to structural instabilities and favors lowsymmetry phases [18]. However, combining 5f-electrons based elements in the first part of the actinide series with some hexagonal p-orbital based lattices may yield delocalized states with linear dispersion close to the Fermi energy where the f-electrons have an important contribution.…”

Section: Introductionmentioning

confidence: 99%

f-Orbital based Dirac states in a two-dimensional uranium compound

López-Bezanilla

2020

J. Phys. Mater.

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Theoretical evidence of the existence of Dirac cones in two-dimensional UB_4 is provided. Dirac cones are created due to the interaction of strongly localized U anisotropic f-orbitals with the delocalized network of B p-orbitals in a bilayer honeycombed lattice. Spin-orbit coupling splits the relativistic electronic states in the vicinity of the Fermi level creating cone-shaped gaped bands. The contribution of f-orbitals to the formation of dispersive Dirac states is clearly determined with several theoretical approximations. U atom provides the exact amount of charge to stabilize the B sublattices creating a heavy-electron based material with reminiscent properties of graphene. The interplay between f-and p-orbitals of U and B atoms, respectively, is revealed as the origin of the itinerant electronic states, defying the paradox of delocalized electrons in a heavy-electron based material. Computed phonon diagram exhibits decoupled acoustic and optic modes arising from U and B atom vibrations, respectively, with frequencies of acoustic modes rather small as compared to optic modes. The dynamical properties of isoelectronic UAl 4 and UGa 4 are also analyzed.

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“…This relaxation has generally a rather weak effect on the actinide volumes, except for α-plutonium where it is significant. In this instance, a structural relaxation contracts the volume substantially relative to a calculation where the experimental (room-temperature) structure is assumed [40,46].…”

Section: Methodsmentioning

confidence: 99%

“…In these reports, a variety of U parameters are chosen, but a small U has largely been favored (U~1 eV). Exceptions are investigations focused on δ-plutonium, where larger U's have often been adopted (U > 4 eV), as has been discussed thoroughly in a recent review paper [40].…”

Section: Introductionmentioning

confidence: 99%

Assessing Relativistic Effects and Electron Correlation in the Actinide Metals Th to Pu

et al. 2019

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Density functional theory (DFT) calculations are employed to explore and assess the effects of the relativistic spin-orbit interaction and electron correlations in the actinide elements. Specifically, we address electron correlations in terms of an intra-atomic Coulomb interaction with a Hubbard U parameter (DFT + U). Contrary to recent beliefs, we show that for the ground-state properties of the light actinide elements Th to Pu, the DFT + U makes its best predictions for U = 0. Actually, our modeling suggests that the most popular DFT + U formulation leads to the wrong ground-state phase for plutonium. Instead, extending DFT and the generalized gradient approximation (GGA) with orbital-orbital interaction (orbital polarization; OP) is the most accurate approach. We believe the confusion in the literature on the subject mostly originates from incorrectly accounting for the spin-orbit (SO) interaction for the p 1/2 state, which is not treated in any of the widely used pseudopotential plane-wave codes. Here, we show that for the actinides it suffices to simply discard the SO coupling for the p states for excellent accuracy. We thus describe a formalism within the projector-augmented-wave (PAW) scheme that allows for spin-orbit coupling, orbital polarization, and non-collinear magnetism, while retaining an efficient calculation of Hellmann-Feynman forces. We present results of the ground-state phases of all the light actinide metals (Th to Pu). Furthermore, we conclude that the contribution from OP is generally small, but substantial in plutonium.

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Density-functional theory for plutonium

Cited by 54 publications

References 124 publications

Nature of the 5f electronic structure of plutonium

Nature of the 5f electronic structure of plutonium

f-Orbital based Dirac states in a two-dimensional uranium compound

Assessing Relativistic Effects and Electron Correlation in the Actinide Metals Th to Pu

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