Vibrational spectra, phase transitions and force-fields in crystalline scandium hexafluorides

Abstract The combined Raman, crystallographic and thermal data confirm the existence of two tetragonal and one cubic phase for the M 3 ScF 6 (MRb, Cs, Tl) compounds. Normal-coordinate calculations suggest that the tetragonal→tetragonal rearrangement results from a decrease in the cation-F interaction, thus yielding two octahedra with more similar environments. The tetragonal→cubic transition results in a crystal with all Sc-F bonds equivalent.