Theoretical studies of the actinides: method calibration for the UO22+ and PuO22+ ions

Ismail, Nina; Heully, Jean‐Louis; Saue, Trond; Daudey, J. P.; Marsden, Colin J.

doi:10.1016/s0009-2614(98)01394-3

Cited by 116 publications

(148 citation statements)

References 25 publications

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“…Hay and Martin [23] found that one could adequately describe the electronic and geometric properties of actinide complexes without treating spin-orbit effects explicitly. Similar conclusions have been reached by Ismail et al [24] in their study of uranyl and plutonyl ions. We also note, as mentioned before, that scalarrelativistic hybrid density functional theory has been used by Kudin et al [15] to describe the insulating gap of UO 2 , yielding a correct anti-ferromagnetic insulator.…”

Section: B Computational Details and Resultssupporting

confidence: 89%

Density functional study of O₂ adsorption on (100) surface of γ‐uranium

Huda

Ray

2004

Int J of Quantum Chemistry

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We have studied the chemisorption processes of O 2 on the (100) surface of uranium using generalized gradient approximation to density functional theory. Dissociative adsorptions of O 2 are significantly favored compared to molecular adsorptions. We found interstitial adsorption of molecular oxygen to be less probable, as no bound states were found in this case. Upon oxygen adsorption, O 2p orbitals is found to hybridize with U 5f bands, and part of the U 5f electrons become more localized. Also there is a significant charge transfer from the first layer of the uranium surface to the oxygen atoms, which made the bonding partly ionic. For the most favored site the dissociative chemisorption energy is approximately 9.5 eV, which indicates a strong reaction of uranium surface with oxygen. Spin polarization does not have a considerable effect on the chemisorption process. For most of the sites and approaches, chemisorption configurations are almost same at both spin-polarized and non-spin-polarized cases. For the most favored chemisorption sites of oxygen on uranium, paramagnetic adsorption is slightly stronger, by 0.304 eV, than the magnetic adsorption.

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Section: B Computational Details and Resultssupporting

confidence: 89%

Density functional study of O₂ adsorption on (100) surface of γ‐uranium

Huda

Ray

2004

Int J of Quantum Chemistry

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“…It has been shown that the large-core RECPs in conjunction with DFT can provide unrealistic structures. [57][58][59][60] We note that because of the high number of low-lying electronic states found for PuC, only a selection of characteristic states is listed in Table IV. More detailed information on the SF and SO states at the two bond distances considered (1.913 and 1.898 Å, respectively) can be found in the supplementary material (Tables S4 and S5).…”

Section: B So Calculations and Electronic Spectramentioning

confidence: 99%

Theoretical study of actinide monocarbides (ThC, UC, PuC, and AmC)

Pogány

Kovács

Visscher

et al. 2016

The Journal of Chemical Physics

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A study of four representative actinide monocarbides, ThC, UC, PuC, and AmC, has been performed with relativistic quantum chemical calculations. The two applied methods were multireference complete active space second-order perturbation theory (CASPT2) including the Douglas-Kroll-Hess Hamiltonian with all-electron basis sets and density functional theory with the B3LYP exchange-correlation functional in conjunction with relativistic pseudopotentials. Beside the ground electronic states, the excited states up to 17 000 cm−1 have been determined. The molecular properties explored included the ground-state geometries, bonding properties, and the electronic absorption spectra. According to the occupation of the bonding orbitals, the calculated electronic states were classified into three groups, each leading to a characteristic bond distance range for the equilibrium geometry. The ground states of ThC, UC, and PuC have two doubly occupied π orbitals resulting in short bond distances between 1.8 and 2.0 Å, whereas the ground state of AmC has significant occupation of the antibonding orbitals, causing a bond distance of 2.15 Å.

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“…[11,12] Several density functional theory (DFT) calculations have been performed on plutonium complexes such as oxides in the past. [9,[13][14][15][16][17][18][19] However, albeit DFT is in principle capable of treating open-shell molecules with multi-reference character, [20] it is known that the currently available density functional approximations often perform poorly in such cases. [12,21] It is therefore preferable to employ from the outset multireference approaches such as the Complete-Active-Space Self-Consistent-Field (CASSCF) method and the Density Matrix Renormalization Group (DMRG) algorithm [22][23][24][25][26][27][28][29][30][31] in order to obtain a qualitatively correct zeroth-order wave function for these systems.…”

Section: Introductionmentioning

confidence: 99%

“…[51] The considerable body of work on actinyl species such as PuO 2+ 2 has allowed us to be confident in our understanding of their electronic structure and the nature of the actinide-oxygen bond. [13,17,[52][53][54] Using molecular orbital diagrams and accounting for point group symmetry, plutonium and oxygen can form σ and π bonds with doubly occupied orbitals up until the 3σ u orbital. With the 5f and 6d orbitals being in the primary valence shell, actinides are able to form unique bonds and interact with other compounds in ways that no other elements are able to.…”

Section: Introductionmentioning

confidence: 99%

On the multi-reference nature of plutonium oxides: PuO₂²⁺, PuO₂, PuO₃ and PuO₂(OH)₂

Boguslawski

Réal

Tecmer

et al. 2017

Phys. Chem. Chem. Phys.

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Actinide-containing complexes present formidable challenges for electronic structure methods due to the large number of degenerate or quasi-degenerate electronic states arising from partially occupied 5f and 6d shells. Conventional multi-reference methods can treat active spaces that are often at the upper limit of what is required for a proper treatment of species with complex electronic structures, leaving no room for verifying their suitability. In this work we address the issue of properly defining the active spaces in such calculations, and introduce a protocol to determine optimal active spaces based on the use of the Density Matrix Renormalization Group algorithm and concepts of quantum information theory. We apply the protocol to elucidate the electronic structure and bonding mechanism of volatile plutonium oxides (PuO 3 and PuO 2 (OH) 2 ), species associated with nuclear safety issues for which little is known about the electronic structure and energetics. We show how, within a scalar relativistic framework, orbital-pair correlations can be used to guide the definition of optimal active spaces which provide an accurate description of static/non-dynamic electron correlation, as well as to analyse the chemical bonding beyond a simple orbital model. From this bonding analysis we are able to show that the addition of oxo-or hydroxo-groups to the plutonium dioxide species considerably changes the pi-bonding mechanism with respect to the bare triatomics, resulting in bent structures with considerable multi-reference character.

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Theoretical studies of the actinides: method calibration for the UO22+ and PuO22+ ions

Cited by 116 publications

References 25 publications

Density functional study of O₂ adsorption on (100) surface of γ‐uranium

Density functional study of O₂ adsorption on (100) surface of γ‐uranium

Theoretical study of actinide monocarbides (ThC, UC, PuC, and AmC)

On the multi-reference nature of plutonium oxides: PuO₂²⁺, PuO₂, PuO₃ and PuO₂(OH)₂

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Theoretical studies of the actinides: method calibration for the UO22+ and PuO22+ ions

Cited by 116 publications

References 25 publications

Density functional study of O2 adsorption on (100) surface of γ‐uranium

Density functional study of O2 adsorption on (100) surface of γ‐uranium

Theoretical study of actinide monocarbides (ThC, UC, PuC, and AmC)

On the multi-reference nature of plutonium oxides: PuO22+, PuO2, PuO3 and PuO2(OH)2

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Density functional study of O₂ adsorption on (100) surface of γ‐uranium

Density functional study of O₂ adsorption on (100) surface of γ‐uranium

On the multi-reference nature of plutonium oxides: PuO₂²⁺, PuO₂, PuO₃ and PuO₂(OH)₂