In situ high temperature Raman and DFT analysis of cerium fluoride and oxyfluoride structures in molten FLiNaK

Abstract In order to investigate the species in the FLiNaK–CeF 3 and FLiNaK–CeF 3 –Li 2 O melts, in situ high temperature Raman spectroscopy was used with the aid of density functional theory (DFT) calculation. In molten FLiNaK, the CeF 6 3− octahedra affected by alkali cations were identified to be the predominan species. Binuclear cerium oxyfluoride anions Ce 2 OF 8 4− and Ce 2 OF 10 6− were formed after adding O 2− into the molten FLiNaK‐CeF 3 (20 mol%) mixtures. Both of these two species were predicted to have Ce−O−Ce geometries with two CeF 4 /CeF 5 moieties bridged by a single oxygen atom.