Symmetry analysis of calculated vibrational spectra of Rb2KScF6 crystal

To interpret the recent results of Raman scattering soft mode below phase transitions in Rb2KScF6 elpasolite-like crystal, results of ab initio simulations of its lattice dynamics obtained within modified Gordon-Kim approach, are used. Calculated eigenvectors of lattice normal modes are attributed to experimental lines using projector operator method. It is shown that the complicated behavior of the soft mode in the lower temperature phase of the crystal is due to its interaction with “hard” vibrations of Rb+ ions.