Кл.слова (ненормированные):
(NH4)3TiF7 -- lattice dynamics -- order–disorder -- reconstructive phase transition -- symmetry lowering
Аннотация: Raman spectra of (NH4)3TiF7 within spectral range 10–3,400 cm−1 at temperatures 8–370 K are recorded, which revealed 2 phase transitions at temperatures T1 = 355 K and T2 = 283 K. First principles calculations of lattice dynamics and assignment of the observed lines to specific vibrational types are performed. The first phase transition is classified as an “order–disorder” one. Manifestation of 97 cm−1 vibration (mixed translational [NH4 + F7]) evidences the creation of the hydrogen bond between ammonium group and free fluorine atom, indicating to reconstructive type of phase transition an T2 = 283 K. The emergence of a large number of vibrational lines in Raman spectra at low temperatures proves symmetry lowering of NH4 tetrahedra with the simultaneous ordering of TiF6 octahedra.
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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russian Federation
Institute of Chemistry, Far Eastern Branch of RAS, Vladivostok, Russian Federation
Amirkhanov Institute of Physics, Dagestan Scientific Center of RAS, Makhachkala, Russian Federation
Ioffe Institute, Russian Academy of Sciences, St.-Petersburg, Russian Federation
St.-Petersburg State University, St.-Petersburg, Russian Federation
Доп.точки доступа:
Gerasimova, Y.V.; Герасимова, Юлия Валентиновна; Oreshonkov, A. S.; Орешонков, Александр Сергеевич; Laptash, N. M.; Krylov, A. S.; Крылов, Александр Сергеевич; Aliev, A. R.; Roginskii, E. M.