Investigation of structure phase transitions in oxyfluoride K 3WO 3F 3

The article presents investigation of vibrational spectra of oxyfluoride K 3WO 3F 3 by Raman technique at different temperatures and under high hydrostatic pressure; the nonempirical lattice dynamics calculation was carried out in framework of generalized Gordon-Kim model. It was shown, that ferroelectric phase in cryolite K 3WO 3F 3 is realized due to displacements of potassium atoms from equilibrium state, as a result of phase transitions at Т1 = 452 K and Т2 = 414 K, but is not due to ordering of anions atoms in octahedron [WO3F3] 3-.