Actinoid(III) Hydration—First Principle Gibbs Energies of Hydration Using High Level Correlation Methods

Heinz, Norah; Zhang, Jun; Dolg, Michael

doi:10.1021/ct5007339

Cited by 31 publications

(46 citation statements)

References 36 publications

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“…As organic phase n-heptane and kerosene were assumed for HC272 and HC301, respectively. 5 Applying recently published hydration Gibbs free energies for Eu 3+ (À3386 kJ mol À1 ) 55 and Am 3+ (À3281 kJ mol À1 ) 55 calculated at the CCSD(T) level by means of the incremental scheme, the obtained absolute values (Eu 3+ 141.1 kJ mol À1 ; Am 3+ 120.2 kJ mol À1 ) disagree within 80 kJ mol À1 with the experimental data, whereas the correct trend is kept. For H + , the experimental value DG aqu (H + ) = À1104.5 kJ mol À1 was used in both cases.…”

Section: Discussionmentioning

confidence: 88%

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Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272

Cao

Zhang

Weißmann

et al. 2015

Phys. Chem. Chem. Phys.

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The experimentally observed extraction complexes of trivalent lanthanide Eu(3+) and actinide Am(3+)/Cm(3+) cations with Cyanex272 [bis(2,4,4-trimethylpentyl) phosphinic acid, denoted as HC272] and Cyanex301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid, denoted as HC301] have been studied by using relativistic energy-consistent 4f- and 5f-in-core pseudopotentials for trivalent f elements, combined with density functional theory and a continuum solvation model. It has been found that, as a result of hydrogen bonding, HC272 exists primarily as a self-associated species, whereas HC301 is preferably a monomer. The calculations show that in case of all three M(3+) (M = Eu, Am, Cm) ions for HC272 the extraction complexes M[H(C272)2]3 are formed prior to M(C272)3, whereas for HC301 the extraction complexes M(C301)3 have priority over M[H(C301)2]3. The calculated M-O and M-S bond lengths and the M-P distances of these preferred extraction complexes agree very well with the available experimental data. The obtained changes of the Gibbs free energies in the liquid-liquid extraction reactions (1): Maqu(3+) + 3(HC272)2,org→ M[H(C272)2]3,org + 3Haqu(+) and (2): Maqu(3+) + 3HC301org→ M(C301)3,org + 3Haqu(+) agree with the experimentally observed thermodynamical priorities of HC272 and HC301, i.e., HC272 prefers Eu(3+) over Am(3+)/Cm(3+) and HC301 prefers Am(3+)/Cm(3+) over Eu(3+). The obtained changes of the Gibbs free energies in reaction (2) (Eu, 68.1 kJ mol(-1); Am, 46.5 kJ mol(-1)) agree quite well with the experimental findings (Eu, 63.3 kJ mol(-1); Am, 44.1 kJ mol(-1)).

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Section: Discussionmentioning

confidence: 88%

“…4 8,9) to obtain the Gibbs free hydration energies for lanthanoid(III) 54 and actinoid(III) 55 ions. For HC272 the obtained DG s and DG e for Eu 3+ are at least 20 kJ mol À1 smaller than those for Am 3+ and Cm 3+ .…”

Section: Change Of the Gibbs Free Energy For M 3+ + 3(hc272) 2 -M[h(cmentioning

confidence: 99%

Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272

Cao

Zhang

Weißmann

et al. 2015

Phys. Chem. Chem. Phys.

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“…27 The geometries of large solvation shell clusters An(H 2 O) 8 25,26 2+/+ (An = U, Np, Pu) have been optimized using the NWChem 33 software package ( Figure 1). Prior work has illustrated the change in accuracy of these solution-phase thermochemical values as a function of the number of explicit waters used in hydrated clusters.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

Sensitivity of Solvation Environment to Oxidation State and Position in the Early Actinide Period

et al. 2015

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The aqueous solvation of U-Pu in the III-VI oxidation states has been examined using density functional theory and hydrated cluster models of the form An(H2O)30(4+/3+) and AnO2(H2O)30(2+/+) embedded within a polarizable continuum model to approximate the effect of bulk water. The structural features are compared to available data from extended X-ray absorption fine structure. Then, using a multiple-scattering approach, the X-ray absorption near-edge spectra (XANES) have been simulated and compared to experiment. These structural data are complemented by a detailed thermodynamic analysis using a recently benchmarked protocol. The structural, spectroscopic, and thermodynamic information has been used to assign the primary solvation environments in water, with an emphasis upon understanding how oxidation state and position in the period modifies the hydration number and equilibrium between different solvation shell environments. Tetravalent U is proposed to exist in equilibrium between the 8- and 9-coordinate species. Moving to the right of the period, Np(IV) and Pu(IV) exist solely as the octa-aquo species. Reduction to the trivalent ions leads to thermodynamic favorability for this solvation environment, whose features reproduce the XANES spectra. The actinyl dications (AnO2(2+)) of U and Np have a preferred environment in the equatorial plane consisting of 5 solvating waters; however, changes to the ionic radius and electronic structure at Pu leads to an equilibrium between the 4- and 5-coordinate species for PuO2(2+). Reduction of the dications to form the monocations generally leads to a preference for the 4-coordinate primary solvation shell, with an equilibrium existing for uranyl, while the neptunyl and plutonyl species exist solely as AnO2(H2O)4(+). These data provide accurate thermodynamic information for several rare species and the combined thermodynamic, structural, and spectroscopic approach reveals trends in hydration behavior across actinide oxidation states and within the early actinide period.

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“…getic correction for hydrogen bonding between the first and second-hydration spheres. 19 The relative energy between the nine and eight-coordinated ions decreases while that between nine and ten-coordinated ions increases as the nuclear charge increases down the actinide series. This trend is further enhanced when the hydrogen-bond correction to the continuum solvation free energy is applied.…”

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confidence: 99%

First structural characterization of Pa(iv) in aqueous solution and quantum chemical investigations of the tetravalent actinides up to Bk(iv): the evidence of a curium break

et al. 2016

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Actinoid(III) Hydration—First Principle Gibbs Energies of Hydration Using High Level Correlation Methods

Cited by 31 publications

References 36 publications

Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272

Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272

Sensitivity of Solvation Environment to Oxidation State and Position in the Early Actinide Period

First structural characterization of Pa(iv) in aqueous solution and quantum chemical investigations of the tetravalent actinides up to Bk(iv): the evidence of a curium break

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Actinoid(III) Hydration—First Principle Gibbs Energies of Hydration Using High Level Correlation Methods

Cited by 31 publications

References 36 publications

Accurate quantum chemical modelling of the separation of Eu3+from Am3+/Cm3+by liquid–liquid extraction with Cyanex272

Accurate quantum chemical modelling of the separation of Eu3+from Am3+/Cm3+by liquid–liquid extraction with Cyanex272

Sensitivity of Solvation Environment to Oxidation State and Position in the Early Actinide Period

First structural characterization of Pa(iv) in aqueous solution and quantum chemical investigations of the tetravalent actinides up to Bk(iv): the evidence of a curium break

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Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272

Accurate quantum chemical modelling of the separation of Eu³⁺from Am³⁺/Cm³⁺by liquid–liquid extraction with Cyanex272