Origins of the odd optical observables in plutonium and americium tungstates

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  • Justin N. Cross, Los Alamos Natl Lab, United States Department of Energy (DOE), Los Alamos National Laboratory, Plutonium Sci & Mfg Directorate
  • ,
  • Tsung-Han Lee, Rutgers State Univ, Rutgers State University New Brunswick, Dept Phys & Astron
  • ,
  • Chang-Jong Kang, Rutgers State Univ, Rutgers State University New Brunswick, Dept Phys & Astron
  • ,
  • Yong-Xin Yao, Iowa State Univ, Iowa State University, United States Department of Energy (DOE), Ames National Laboratory, Ames Lab, US DOE
  • ,
  • Samantha K. Cary, Los Alamos Natl Lab, United States Department of Energy (DOE), Los Alamos National Laboratory, Plutonium Sci & Mfg Directorate
  • ,
  • Jared T. Stritzinger, Los Alamos Natl Lab, United States Department of Energy (DOE), Los Alamos National Laboratory, Plutonium Sci & Mfg Directorate
  • ,
  • Matthew J. Polinski, Bloomsburg Univ Penn, Pennsylvania State System of Higher Education (PASSHE), Bloomsburg University of Pennsylvania, Dept Chem & Biochem
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  • Carla D. McKinley, Florida State Univ, State University System of Florida, Florida State University, Dept Chem & Biochem
  • ,
  • Thomas E. Albrecht Schmitt, Florida State Univ, State University System of Florida, Florida State University, Dept Chem & Biochem
  • ,
  • Nicola Lanata

A series of trivalent f-block tungstates, MW2O7(OH)(H2O) (M = La, Ce, Pr, Nd, and Pu) and AmWO4(OH), have been prepared in crystalline form using hydrothermal methods. Both structure types take the form of 3D networks where MW2O7(OH)(H2O) is assembled from infinite chains of distorted tungstate octahedra linked by isolated MO8 bicapped trigonal prisms; whereas AmWO4(OH) is constructed from edge-sharing AmO8 square antiprisms connected by distorted tungstate trigonal bipyramids. PuW2O7(OH)(H2O) crystallizes as red plates; an atypical color for a Pu(iii) compound. Optical absorption spectra acquired from single crystals show strong, broadband absorption in the visible region. A similar feature is observed for CeW2O7(OH)(H2O), but not for AmWO4(OH). Here we demonstrate that these significantly different optical properties do not stem directly from the 5f electrons, as in both systems the valence band has mostly O-2p character and the conduction band has mostly W-5d character. Furthermore, the quasi-particle gap is essentially unaffected by the 5f degrees of freedom. Despite this, our analysis demonstrates that the f-electron covalency effects are quite important and substantially different energetically in PuW2O7(OH)(H2O) and AmWO4(OH), indicating that the optical gap alone cannot be used to infer conclusions concerning the f electron contribution to the chemical bond in these systems.

OriginalsprogEngelsk
TidsskriftChemical Science
Vol/bind10
Nummer26
Sider (fra-til)6508-6518
Antal sider11
ISSN2041-6520
DOI
StatusUdgivet - jul. 2019

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