Combined Approach for the Structural Characterization of Alkali Fluoroscandates: Solid-State NMR, Powder X-ray Diffraction, and Density Functional Theory Calculations.

The structures of several fluoroscandate compounds are presented here using a characterization approach combining powder X-ray diffraction and solid-state NMR. The structure of KScF was fully determined from Rietveld refinement performed on powder X-ray diffraction data. Moreover, the local structures of NaScF, LiScF, KScF, and NaScF compounds were studied in detail from solid-state F and Sc NMR experiments. The Sc chemical shift ranges for six- and seven-coordinated scandium environments were defined. The F chemical shift ranges for bridging and terminal fluorine atoms were also determined. First-principles calculations of the F and Sc NMR parameters were carried out using plane-wave basis sets and periodic boundary conditions (CASTEP), and the results were compared with the experimental data. A good agreement between the calculated shielding constants and experimental chemical shifts was obtained. This demonstrates the good potential of computational methods in spectroscopic assignments of solid-state Sc NMR spectroscopy.