Actinyl chemistry at the Centre for Radiochemistry Research

May, Iain; Copping, Roy; Cornet, Stéphanie M.; Talbot-Eeckelears, Catherine E.; Gaunt, Andrew J.; John, Gordon H.; Redmond, Mike P.; Sharrad, Clint A.; Sutton, Andrew D.; Collison, David; Fox, Olivia; Jones, Chris J.; Sarsfield, Mark J.; Taylor, Raymond L.

doi:10.1016/j.jallcom.2006.10.110

Cited by 6 publications

(8 citation statements)

References 39 publications

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“…An alternative to incorporate electron correlation is to construct a coupled cluster wave function (CC) with the coupled-pair approximation, 135 which takes the HF wavefunction as the zeroth order reference and accounts for the coupling of correlated electron pairs through the expansion of an exponential operator, exp(T ˆ), with T ˆthe excitation operator. It has been suggested that at present the best trade-off of accuracy and efficiency is CCSD(T), which treats the triplet excitations in a perturbative way, and is formally scaled as N 7 where N is the number of electrons. 128 The Fock-space coupled cluster (FSCC) method, which is a multireference variant of the CC method, has been proven to be able to predict accurate transition energies between electronic states of a wide range of atomic and molecular systems.…”

Section: Wavefunction Based Ab Initio Methodsmentioning

confidence: 99%

“…In a PBE study, Wu and Lu 251 found a triple bond between the two U atoms that are embedded in C 60 , and the configuration includes six 2-center 1-electron orbitals (5fp u ) 2 (5fs g ) 1 (5fd g ) 2 (5ff u ) 1 . The ground state of U 2 @C 60 (I h ) is characterized as 7 A 2u , and the valence state is [U 2 ] 6+ @C 60 6À or [U 3+ ] 2 @C 60…”

Section: Metal-metal Bondmentioning

confidence: 99%

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Recent advances in computational actinoid chemistry

2012

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We briefly review advances in computational actinoid (An) chemistry during the past ten years in regard to two issues: the geometrical and electronic structures, and reactions. The former addresses the An-O, An-C, and M-An (M is a metal atom including An) bonds in the actinoid molecular systems, including actinoid oxo and oxide species, actinoid-carbenoid, dinuclear and diatomic systems, and the latter the hydration and ligand exchange, the disproportionation, the oxidation, the reduction of uranyl, hydroamination, and the photolysis of uranium azide. Concerning their relevance to the electronic structures and reactions of actinoids and their importance in the development of an advanced nuclear fuel cycle, we also mentioned the work on actinoid carbides and nitrides, which have been proposed to be candidates of the next generation of nuclear fuel, and the oxidation of PuO(x), which is important to understand the speciation of actinoids in the environment, followed by a brief discussion on the urgent need for a heavier involvement of computational actinoid chemistry in developing advanced reprocessing protocols of spent nuclear fuel. The paper is concluded with an outlook.

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Section: Wavefunction Based Ab Initio Methodsmentioning

confidence: 99%

Section: Metal-metal Bondmentioning

confidence: 99%

Recent advances in computational actinoid chemistry

2012

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“…2 This linear trans-dioxo cation is the most common configuration found for the high-valent, early actinides in the penta-or hexavalent states from uranium to americium. 3,4 The strength of AnvO yl bonds are important to understanding the chemistry of these systems and is the subject of extensive experimental and theoretical studies to understand its electronic structure. [5][6][7][8][9][10][11][12] In addition, this particular bonding motif imparts significant influence on the chemistry in aqueous and solid-state systems, resulting in overall changes in its redox properties, 13,14 disproportionation reactions, 15 and complex vibrational and electronic spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Use of vibrational spectroscopy to identify the formation of neptunyl–neptunyl interactions: a paired density functional theory and Raman spectroscopy study

et al. 2022

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“…However, the nuclear charge and formal valence of Th 4+ are lower than those of U 6+ , resulting in less interaction of the lowest-unoccupied Th orbitals with valence orbitals, and no destabilization of relatively isotropic coordination geometry, as seen in the ThO 8À9 polyhedra of minerals such as the thorite and huttonite polymorphs of ThSiO 4 , which resemble those of Zr 4+ and the larger, lighter lanthanides such as Ce 3+ in zircon and monazite, respectively (Taylor and Ewing, 1978). Heavier actinides such as Np and Pu might well behave similarly to U as they form similar MO 2 n+ cationic complexes (Krivovichev et al, 2007;May et al, 2007), but occur in the crust at concentrations too small to form their own species.…”

Section: Actinidesmentioning

confidence: 99%

Causes of anomalous mineralogical diversity in the Periodic Table

Christy

2015

Mineral. mag.

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When crustal abundance (A, measured in atomic parts per million) of a chemical element is plotted vs. number of mineral species in which that element is an essential constituent (S), a significantly positive correlation is obtained, but with considerable scatter. Repeated exclusion of outliers at the 90% confidence level and re-fitting leads, after the sixth iteration, to a steady state in which 40 of the 70 elements initially considered define a trend with log S = 1.828 + 0.255 log a (r = 0.96), significantly steeper than the original. Three other methods for reducing the effect of outliers independently reproduce this steeper trend. The 'diversity index' D of an element is defined as the ratio of observed mineral species to those predicted from this trend. D separates elements into three groups. More than half of the elements (40 of 70) have D = 0.5–2.0. Apart from these 'typical' elements, a group of 15 elements (Sc, Cr, Ga, Br, Rb, In, Cs, La, Nd, Sm, Gd, Yb, Hf, Re and Th) form few species of their own due to being dispersed as minor solid solution constituents, and a hitherto unrecognized group of 15 elements are essential components in unusually large numbers of minerals. The anomalously diverse group consists of H, S, Cu, As, Se, Pd, Ag, Sb, Te, Pt, Au, Hg, Pb, Bi and U, with Te and Bi by far the most mineralogically diverse elements (D = 22 and 19, respectively). Possible causes and inhibitors of diversity are discussed, with reference to atomic size, electronegativity and Pearson softness, and particularly outer electronic configurations that result in distinctive stereochemistry. The principal factors encouraging mineral diversity are: (1) Particular outer electronic configurations that lead to a preference for unique coordination geometries, enhancing an element's ability to form distinctive chemical compounds and decreasing its ability to participate in solid solutions. This is particularly noteworthy for elements possessing geometrically flexible 'lone-pair cations' with an s2 outer electronic configuration. (2) Siderophilic or chalcophilic geochemical behaviour and intermediate electronegativity, allowing elements to form minerals that are not oxycompounds or halides. (3) Access to a wide range of oxidation states. The most diverse elements can occur as anions, native elements and in more than one cationic valence state.

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Actinyl chemistry at the Centre for Radiochemistry Research

Cited by 6 publications

References 39 publications

Recent advances in computational actinoid chemistry

Recent advances in computational actinoid chemistry

Use of vibrational spectroscopy to identify the formation of neptunyl–neptunyl interactions: a paired density functional theory and Raman spectroscopy study

Causes of anomalous mineralogical diversity in the Periodic Table

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