Approaching actinide(+III) hydration from first principles

Abstract

A systematic computational approach to An(III) hydration on a density-functional level of theory, using quasi-relativistic 5f-in-core pseudopotentials and valence-only basis sets for the An(III) subsystems, is presented. Molecular structures, binding energies, hydration energies, and Gibbs free energies of hydration have been calculated for [An(III)(OH(2))(h)](3+) (h = 7, 8, 9) and [An(III)(OH(2))(h-1) * OH(2)](3+) (h = 8, 9), using large (7s6p5d2f1g)/[6s5p4d2f1g] An(III) and cc-pVQZ O and H basis sets within the COSMO implicit solvation model. An(III) preferred primary hydration numbers are found to be 8 for all An(III) at the gradient-corrected density-functional level of theory. Second-order Møller-Plesset perturbation theory predicts preferred primary hydration numbers of 9 and 8 for Ac(III)-Md(III) and No(III)-Lr(III), respectively.

Quasirelativistic energy-consistent 5f-in-core pseudopotentials for trivalent actinide elements

“…A similar statement holds for yet unpublished studies of the hydration behaviour of trivalent actinide ions [18]. Moreover, unpublished CCSD(T) results of Cao for the vibrational frequencies of UF 3 obtained with the 5f-in-core approach are within the experimental error bars.…”

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf3+

“…If these data are excluded, the standard deviation goes down to 0.09 Å. The resulting classical structures for the octa-and ennea-hydrated ion are in good agreement not only with our quantum optimized hydrated ion but also with previous quantum results published by Dolg et al 43 (2.495 Å for the octahydrated and 2.537 Å for the enneahydrated ion). Moreover, when we consider the hydrated ion with its second solvation shell, the distance and orientation agreement is remarkable, as shown in Figure 6, where MP2 optimized structures are compared with those optimized with the Pot_Bb potential.…”

“…Previous studies including quantum mechanical calculations of the aqua ion series of actinoids support this assumption. 43 Because of the large number of structures to be included in the fitting, it seems of interest to provide an idea about the computational cost of the quantum mechanical clusters. …”

DFT modeling of the relative affinity of nitrogen ligands for trivalent f elements: an energetic point of view

“…To date, theoretical studies dedicated to trivalent rare earth complexes have thus been mainly applied to structural data, with very satisfying agreements, but other computational analyses, and notably energetic analyses, have seldom been validated. [39][40][41] Yet, even though structural parameters can account for covalency effects, they cannot differentiate systems on the basis of their relative stability. Only energetic data-complexation constants, free energies-can provide such information and are thus useful to explain the observed selectivity in actinide/ lanthanide extractions.…”