THE NATURE OF ACTINYL-LIGAND BINDING: $AnX^{2-}_{2}$ IONS $(X=S, Se. Te)$ VALENCE-ISOELECTRONIC WITH $AnO^{2|}_{2}$
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Date
1999
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Ohio State University
Abstract
There is substancial current interest in theoretical studies of the actinides, which represent one of the main current challenges for computational chemistry. We have shown that 1-component pseudopotential methods are satisfactory for the uranylion; in particular, DFT methods are highly promising. There does not appear to have been any previous work, either experimental or theoretical, on $AnX^{2+}_{2}$ ions containing the heavier Group 16 elements (S, Se, Te). We find that their electronic and geometrical structures bear little resemblance to those of $AnX^{2+}_{2}$. They have quintet ground states for $An=U$, and are strongly bent, with X-U-X angles of around 50 degres and substantial X-X bonding. As a result of the differences between size and energy of the valence orbitals of S compared to those of O, the predominant bonding interactions in $US^{2+}_{2}$ involve the 6d orbitals on U rather than 5f. While the actinyls are all geometrically similar, the shapes of $US^{2+}_{2}$ and $PuS^{2+}_{2}$ differ appreciably. This observation, together with the novel bonding involved, suggests that these species may have applications as separation agents for the actinides.
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Author Institution: Universit\'{e} P. Sabatier