Insight into the Crystalline Structure of ThF4 with the Combined Use of Neutron Diffraction, 19F Magic-Angle Spinning-NMR, and Density Functional Theory Calculations
Laura Martel (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe)
Elisa Capelli (TU Delft - RST/Reactor Physics and Nuclear Materials)
Monique Body (Le Mans Université, Le Mans)
Marco Klipfel (Kerntechnische Entsorgung Karlsruhe, Eggenstein-Leopoldshafen)
Ondrej Beneš (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe)
Louis Maksoud (Université d'Orléans)
Phillipe E. Raison (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe)
Emmanuelle Suard (Institut Laue Langevin)
Lucas Visscher (Vrije Universiteit Amsterdam)
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Abstract
Because of its sensitivity to the atomic scale environment, solid-state NMR offers new perspectives in terms of structural characterization, especially when applied jointly with first-principles calculations. Particularly, challenging is the study of actinide-based materials because of the electronic complexity of the actinide cations and to the hazards due to their radioactivity. Consequently, very few studies have been published in this subfield. In the present paper, we report a joint experimental-theoretical analysis of thorium tetrafluoride, ThF4, containing a closed-shell actinide (5f0) cation. Its crystalline structure has been revisited in the present work using powder neutron diffraction experiments. The 19F NMR parameters of the seven F crystallographic sites have been modeled using an empirical superposition model, periodic first-principles calculations, and a cluster-based all-electron approach. On the basis of the atomic position optimized structure, a complete and unambiguous assignment of the 19F NMR resonances to the F sites has been obtained.