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Title: Mixed uranium chloride fluorides UF{sub 6{minus}n}Cl{sub n} and methoxyuranium fluorides UF{sub 6{minus}n}(OCH{sub 3}){sub n}: A theoretical study of equilibrium geometries, vibrational frequencies, and the role of the f orbitals

The title compounds, the uranium (VI) fluoride chlorides (UF{sub 6{minus}n}Cl{sub n}, n = 0--6) and methoxyuranium (VI) fluorides [UF{sub 6{minus}n}(OCH{sub 3}){sub n}, n = 0--5], have been studied using relativistic density functional theory. Applying the B3LYP hybrid functional and an effective core potential on uranium, equilibrium, geometries have been calculated for these molecules. In addition, harmonic vibrational frequencies have been computed for the chloride fluorides. Calculated frequencies have been compared to experiment where possible. All experimentally observed bands have been assigned, based on these calculations. The average deviation between theoretical and experimental frequencies is 15.6 cm{sup {minus}1} for 23 experimental modes. Theory always underestimates the experimental frequencies. This can be explained by the calculated bond lengths that are somewhat too long. The electronic structure of the uranium (VI) chloride fluorides has been investigated using scalar relativistic calculations and the PW91 functional. Periodic trends in the role and bonding contribution of the uranium 5f orbitals are discussed.
Authors:
Publication Date:
OSTI Identifier:
20023362
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 39; Journal Issue: 6; Other Information: PBD: 20 Mar 2000
Research Org:
Los Alamos National Lab., NM (US)
Sponsoring Org:
US Department of Energy
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; URANIUM FLUORIDES; URANIUM CHLORIDES; METHOXY RADICALS; EQUILIBRIUM; MORPHOLOGY; VIBRATIONAL STATES; ELECTRONIC STRUCTURE