Plutonium Oxidation States in Complex Molecular Solids

Ao, Bingyun; Qiu, Ruizhi; Hu, Shu‐Xian

doi:10.1021/acs.jpcc.9b01527

Cited by 21 publications

(16 citation statements)

References 45 publications

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“…My recent calculations support the former configuration, consistent with the observations from X-ray photoemission spectroscopy (XPS) . Additionally, the chemical states of other Ce- and Pu-based ternary oxides have been successfully predicted, which really boosts my confidence in obtaining the atom-resolved chemical states in multivalent U-TM-O ternary oxides. − …”

Section: Introductionsupporting

confidence: 70%

“…The strongly correlated Hubbard model is used to treat open shell TMs d (3d, 4d, 5d) and U 5f electrons within the DFT + U scheme in the Dudarev formalism . In view of my previous and other researchers’ works, the effective Hubbard U eff ( U eff = U – J , i.e., the difference between Coulomb U and exchange J values, hereafter described as U ) values for U 5f electrons is selected as 4 eV. ,,,,− A universal U value ( U = 4 eV) is adopted for the considered TMs to explore the general trend of OS, albeit the literature U values of TMs commonly varying in the range of 2–6 eV. It should be emphasized that the calculation verifications on U values of U and TMs are not particularly meaningful because one specific U value might just satisfy the reproduction of one specific property in one specific compound.…”

Section: Computational Detailsmentioning

confidence: 99%

“…In this regard, I use the orbital occupation number (ON) method which was successful in qualitatively determining quantum-mechanic OS (hereafter denoted as OS qm to distinguish OS f ) of d-block metals and I have extended it to f-block elements . For clarity, I decide to discard the descriptions of the computational details which can be referred to my previous theoretical works. ,,− Herein, I just take UO 2 as the illustration. The calculated ONs of fully occupied 5f orbitals of each U ion in UO 2 are 2, indicative of two 5f electrons not participating in chemical bonding; consequently, one can assign a robust U 4+ because the outer valence electron configuration of U is 5f 3 6d 1 7s 2 and the high-lying itinerant 6d 1 7s 2 electrons and one 5f electron donate to O to form U–O bonds.…”

Section: Computational Detailsmentioning

confidence: 99%

“…On the other hand, the integral OS albeit physically ill-defined, is widely used in solid-state U chemistry and hence discussed in the present work. What is particularly noteworthy is that OS of multivalent metal ions in the complicated solid-state compounds cannot be assigned in terms of ionic limitation (i.e., the formal OS (OS f ) according to IUPAC definition). − In order to overcome the bottleneck, a physically more rational first-principles scheme based on counting occupation numbers of open d or f orbitals has been developed and successfully applied in a variety of 4f and 5f solid materials. ,,− Thus, in the present paper, I utilize this method for clarifying the atom-resolved OS in U-TM-O ternary oxides, aiming at understanding the correlation among composition, structure, and OS.…”

Section: Introductionmentioning

confidence: 99%

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Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

2019

J. Phys. Chem. C

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Uranium (U) has attracted considerable fundamental and applied studies; among them, the rigorous determination of its chemical state is one of the crucial topics owing to its well-known multivalent feature associated with complicated chemical bonding. However, the related studies on solid-state U ternary or beyond ternary compounds are quite in lack. Herein, first-principles DFT + U calculations are performed to unambiguously determine the actual oxidation states of metal ions in U ternary oxides containing multivalent transition-metals (TMs: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W). For the first time, the actual oxidation states of U and TM in the ternary oxides are obtained in a quantitative and atom-resolved manner, thereby providing their nominal compositions. The results disclose the variations of U oxidation states with TM's properties, chemical surrounding, local structure, and oxygen vacancy. In terms of charge transfer, electronic structure, orbital energy level, and oxygen vacancy effect, I conclude that the oxidation state is the competitive consequence of those electronic and structural factors and that electron-structure-related factors play more important roles. Because of the increasing orbital expansion from 3d to 4d and 5d TMs, the latter TMs (Nb, Mo, W) have the greater tendency to form high oxidation states and suppress the formation of high oxidation states of U. On the contrary, 3d TMs, especially Cr, Mn, Fe, and Ni, tend to adopt low oxidation states, thereby promoting the emergence of high oxidation states of U.

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Section: Introductionsupporting

confidence: 70%

Section: Computational Detailsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

2019

J. Phys. Chem. C

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“…Plutonium (Pu) is a key material in the nuclear industry for both energy production and nuclear explosives. − During the extended storage, transport, and safe handling of Pu metal, the reactive Pu sample inevitably suffers environment-dependent chemical corrosions in experimental setups, among which the surface hydrogenation is problematic due to the Pu-hydride product being able to catalyze violently exothermic oxidation reactions with Pu and even induce pyrophoricity, , which is significantly associated with the structure particularity of plutonium hydrides. However, it is very difficult to directly characterize the crystal structure in experiments since Pu-hydride products are extremely reactive and potentially more dangerous than metallic Pu .…”

Section: Introductionmentioning

confidence: 99%

Phase Diagram and Bonding States of Pu–H Binary Compounds at High Pressures

Zhao

et al. 2020

J. Phys. Chem. C

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The high-pressure processes of plutonium hydrides are usually involved in many practical situations, such as the volume expansion during the hydride formation, the pressure of helium bubbles due to the decay of plutonium, and the stress due to the formation of the oxide film. These cases could lead to the high-pressure phase transition of plutonium hydrides and thereby affect the properties of the material. The crystal structure and bonding properties of plutonium hydrides (PuH 1−10 ) under atmospheric pressure and high pressure are investigated by using the first-principle method in combination with a structure searching technique. Our results show that the predicted lattice structures of plutonium hydrides are stable over the given pressure range. A novel stable stoichiometry, PuH with space groupFm3̅ m, is thermodynamically, dynamically, and mechanically stable in the pressure range of 62−188 GPa, which may be synthesized through the pressure-induced disproportionation of PuH 2 . In particular, our theoretically predicted results indicate that PuH 3 undergoes pressure-induced phase transitions with the following sequence of phases, P6 3 cm → Pnma → R3̅ m → Cmcm, and the corresponding transition pressures are computed to be 4, 76, and 150 GPa, respectively. Interestingly, the most striking feature of PuH 3 is the pressure-induced transition from insulating to metallic forms. Analysis of the electric structures, charge density differences, and electronic localization functions indicates that all phases act mainly as metallic with ionic bonding at high pressure.

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Site‐dependent correlation strength and occupation number of 5f electrons in alpha phase plutonium metal

Lü

Xin

et al. 2023

Int J of Quantum Chemistry

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In order to quantify the site‐dependent correlation strengths in terms of the quasi‐particle weights and the occupation numbers of 5f electrons in alpha phase plutonium metal with eight crystallographically nonequivalent atomic sites Pun (n = 1–8), we perform a first principles calculation by using a many‐body method merging density functional theory with dynamical mean‐field theory plus the relativistic and correlation effects. The quasi‐particle weight, the electronic spectrum function, the hybridization function, as well as the occupation number of Pu 5f electrons all suggest that Pu1 and Pu8 atoms have the most itinerant and the most localized 5f electrons, respectively, while the other atoms Pun (n = 2–7) exhibit an intermediate correlation strength. The quasi‐particle weights demonstrate that only the jj or intermediate coupling scheme is more appropriate for Pu 5f electrons in comparison with the Russel–Saunders (LS) scheme. The electronic spectrum function and the occupation analysis establish that Pu 5f electrons simultaneously have dual itinerant and localized regimes with average 5f occupation numbers of n5f between 4.8994 and 4.9628, which are mainly composed of 5f4, 5f5, and 5f6 configurations, irrespective of different atomic sites. Finally, we also estimate the so‐called quasi‐particle band structure to directly compare with angle‐resolved photoemission spectrum.

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Plutonium Oxidation States in Complex Molecular Solids

Cited by 21 publications

References 45 publications

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Atom-Resolved Chemical States in the Multivalent U-TM-O (TM: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W) Ternary Oxides from First-Principles

Phase Diagram and Bonding States of Pu–H Binary Compounds at High Pressures

Site‐dependent correlation strength and occupation number of 5f electrons in alpha phase plutonium metal

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