Approaching actinide(+III) hydration from first principles

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) (OH2)(h)](3+) (h = 7, 8, 9) and [An(III)(OH2)(h-1) center dot OH2](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 Moller-Plesset perturbation theory predicts preferred primary hydration numbers of 9 and 8 for Ac-III-Md-III and No-III-Lr-III, respectively.