Raman spectroscopic study of natural and synthetic brannerite

Raman spectra of a well-characterized natural brannerite and some synthetic brannerite samples have been collected and analysed. For the first time, all 12 theoretical Raman vibrational modes of CeTi2O6 with brannerite structure have been positively identified by using quantum chemical calculations based on density functional theory (DFT) and assigned to the spectra. For synthetic samples with Y or Ca substitution on the U site and Fe substitution on the Ti site, Y-O, Fe-O and U-O vibrational modes are tentatively assigned. The U-O bond lengths for the uranyl (UO2)2+ groups, have been calculated by using the measured wavenumbers of ν1 (UO2)2+ symmetric stretching vibrations and compared with the published U-O bond lengths of a natural brannerite.