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Title: Characterization of pentavalent and hexavalent americium complexes in nitric acid using X-ray absorption fine structure spectroscopy and first-principles modeling

We studied the speciation of pentavalent and hexavalent americium (Am) complexes in nitric acidicby X-ray absorption fine structure spectroscopy (XAFS), UV-visible spectroscopy, and density functional theory (DFT). Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) results were consistent with the presence of a mixture of AmO 2 + and AmO 2 2+ with only a small amount AmO 2 present. The resulting average bond distances we found were 1.71 Å for Am=O and 2.44 Å for Am-O. All-electron scalar relativistic calculations were also carried out using DFT to predict the equilibrium geometries and properties of the AmO 2 + and AmO 2 2+ aquo complexes. Calculated bond distances for the Am(VI) complex are in reasonable agreement with EXAFS data and the computed energy gaps between frontier molecular orbitals suggest a slightly higher kinetic stability and chemical hardness of Am(VI) compared to Am(V).
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [2] ;  [6]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Chemistry
  3. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Physics and Astronomy
  4. Dept. of Energy (DOE), Washington, DC (United States)
  5. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
  6. Soleil, Paris (France)
Publication Date:
Report Number(s):
INL/JOU-15-36872
Journal ID: ISSN 0236-5731; PII: 4704
Grant/Contract Number:
AC07-05ID14517; AC07-99ID13727; AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Radioanalytical and Nuclear Chemistry
Additional Journal Information:
Journal Volume: 309; Journal Issue: 3; Journal ID: ISSN 0236-5731
Publisher:
Springer
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE); USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; Acidic Solution; Americium; Density Functional Theory; Oxidation; X-ray Absorption Fine Structure
OSTI Identifier:
1357492