Тип публикации: статья из журнала
Год издания: 2018
Идентификатор DOI: 10.1002/jrs.5374
Ключевые слова: (NH4)(3)TiF7, lattice dynamics, order-disorder, reconstructive phase transition, symmetry lowering
Аннотация: Raman spectra of (NH4)(3)TiF7 within spectral range 10-3,400cm(-1) at temperatures 8-370K are recorded, which revealed 2 phase transitions at temperatures T-1=355K and T-2=283K. First principles calculations of lattice dynamics and assignment of the observed lines to specific vibrational types are performed. The first phase transitПоказать полностьюion is classified as an order-disorder one. Manifestation of 97cm(-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 T-2=283K. 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.
Журнал: JOURNAL OF RAMAN SPECTROSCOPY
Выпуск журнала: Vol. 49, Is. 7
Номера страниц: 1230-1235
ISSN журнала: 03770486
Место издания: HOBOKEN
Издатель: WILEY