Computational Studies of Uranium Hexafluoride Interacting with Functionalized Organics. I. Screening Intermolecular Potentials between UF₆ and Small Organic Functional Groups

Abstract

We report the intermolecular binding energies (IBEs) between UF6 and over 50 different functionalized small organic molecules as predicted by electronic structure calculations. Optimized geometries of UF6–molecule dimers were found at the MP2/aug-cc-pwCVDZ (non-U), cc-pVDZ-PP (U) level. IBEs were calculated using MP2 and dispersion-corrected DFT theory. We characterize the various functional groups based on the inclusion of specific heteroatoms. Those functional groups containing “nitrogen only” heteroatoms result in larger IBEs than groups containing both nitrogen and oxygen or oxygen alone. Halogen-containing and regular hydrocarbon molecules show the lowest IBEs with UF6. Nonorganic phosphoryl species are also shown to display large IBEs with UF6. These interactions are characterized in part by how much the impinging functionalized molecule distorts the UF6 from its optimal octahedral geometry. Of all the investigated groups, the amine group displayed the largest IBE values (IBE ∼ >12–14 kcal/mol for methyl amine), while hydrocarbons and perfluorocarbons both showed the weakest interactions (IBE ∼ 0.5–1.5 and 0.1–0.8 kcal/mol for methane and perfluoromethane, respectively). The study examines how the strength of the IBE is contingent on a combination of conformational deformation, stabilizing nonbonding interactions, and sterics.

A Computational Study on Closed‐Shell Molecular HexafluoridesMF6(M=S, Se, Te, Po, Xe, Rn, Cr, Mo, W, U) – Molecular Structure, Anharmonic Frequency Calculations, and Prediction of the NdF6Molecule

“…The Actinoid Hexafluoride UF 6 One of the theoretically most extensively studied molecular hexafluorides is UF 6 . [59,[62][63][64]79,82,[88][89][90][91][92][93][94][95][96][97][98][99][100][101][102] The point group of the molecule is O h with an experimentally determined UÀ F bond length of 1.9962 (7) Å. [103] A selection of calculated bond lengths at different levels of theory with their respective reference are listed in Table 1.…”

“…One of the theoretically most extensively studied molecular hexafluorides is UF 6 [59,62–64,79,82,88–102] . The point group of the molecule is O h with an experimentally determined U−F bond length of 1.9962(7) Å [103] .…”

Periodic trends in trivalent actinide halides, phosphates, and arsenates

“…2,7 Halides of actinides have been synthesized in the past. 16 Uranium hexafluoride [17][18][19][20][21][22][23][24][25][26] and plutonium hexafluoride [27][28][29][30][31] probably are the most studied actinide halides due to their importance in the enrichment of fission material for nuclear applications. [32][33][34] Few reports on actinide phosphates and arsenates, mainly focussing on uranium compounds [35][36][37][38][39] and/ or pre-uranium compounds [40][41][42][43][44][45][46] are available in the literature.…”