Raman and density functional theory studies of lutecium fluoride and oxyfluoride structures in molten FLiNaK

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2021-04, Vol.251, p.119435, Article 119435
• Main Authors: Liu, Xiyan, Li, Yangjuan, Wang, Baozhu, Wang, Chenyang
• Format: Article
• Language: English
• Subjects: DFT; Molten salt; Oxyfluoride; Raman spectroscopy
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2021.119435

[Display omitted] •The structure of cerium fluoride and oxyfluoride was studied by Raman and DFT.•Both LuF52− and LuF63− anions were identified in molten FLiNaK.•Lu2OF84−, Lu2O2F42− and Lu2O2F64− anions were confirmed with the addition of Li2O. Combined with Raman spectroscopy and density functional theory (DFT) calculations, the micro-structures in molten FLiNaK-LuF3 and FLiNaK-LuF3-Li2O systems were studied. Both LuF52− (D3h) and LuF63− (Oh) anions were identified in molten FLiNaK, and their relative content varied with the concentration of LuF3. For regarding the affection of oxygen anion, Li2O was added into the molten FLiNaK-LuF3 (20 mol%) sample. The lutecium oxyfluoride anion Lu2OF84− was firstly formed which possesses a linear LuOLu geometry with two LuF4 moieties bridged by one single oxygen atom. Further increasing the Li2O content to 10 mol% resulted in the formation of two species, which belonged to the Lu2O2F42− and Lu2O2F64− anions. When increased the concentration of Li2O to 20 mol%, a new species appeared which was approximate to the oxide structure.