Raman scattering and phase transitions in (NH4)3TiF7

被引：2

作者：

Gerasimova, Y. V. ^{[1
,2
]}

Oreshonkov, A. S. ^{[1
,2
]}

Laptash, N. M. ^{[3
]}

Krylov, A. S. ^{[1
]}

Aliev, A. R. ^{[4
]}

Roginskii, E. M. ^{[5
,6
]}

机构：

[1] Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia

[2] Siberian Fed Univ, Inst Engn Phys & Radio Elect, Krasnoyarsk 660079, Russia

[3] RAS, Inst Chem, Far Eastern Branch, Vladivostok 690022, Russia

[4] RAS, Dagestan Sci Ctr, Amirkhanov Inst Phys, Makhachkala 367003, Russia

[5] Russian Acad Sci, Ioffe Inst, St Petersburg 194021, Russia

[6] St Petersburg State Univ, St Petersburg 199034, Russia

来源：

JOURNAL OF RAMAN SPECTROSCOPY | 2018年 / 49卷 / 07期

基金：

俄罗斯基础研究基金会;

关键词：

(NH4)(3)TiF7; lattice dynamics; order-disorder; reconstructive phase transition; symmetry lowering; FLUORINATION;

D O I：

10.1002/jrs.5374

中图分类号：

O433 [光谱学];

学科分类号：

0703 ; 070302 ;

摘要：

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 transition 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.

引用

页码：1230 / 1235

页数：6

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