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Lattice Dynamics and Raman Spectra of Rb2KScF6 Eplasolite — Comparative Analysis

Krylova S.N., Vtyurin А. N., Bulou А., Krylov А. S., Zamkova N.G.

Raman spectra of Rb2KScF6 elpasolite crystal have been studied in a wide temperature range, including two transition points: from cubic to tetragonal, and then — to the monoclinic phase. Experimental spectra are compared with results of lattice dynamics simulations of these phases performed within ab initio approach. Several anomalies induced by transitional reconstruction of the crystal lattice were found both in the range of internal vibrations of ScF6 molecular ions and lower frequency lattice vibrations, and their quantitative analysis has been performed. Noticeable interaction of lower frequency internal modes with lattice vibrations is pointed out, as well as strong resonance interaction of rotational soft modes restoring below transition points, with hard low frequency vibrations of rubidium ions sublattice, that complicates spectral picture considerably.

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