Vibrational spectroscopic, optical and thermal properties of a deuterated ferroic crystal, [(CH₂OD)₃CND₃]₂SiF₆鈥擜n experimental and theoretical study

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• 作者：D. Podsiadł ; a^a ; ^{dorota@ifd.uni.wroc.pl} ; O. Czupiń ; ski^b ; M. Rospenk^b ; B. Kosturek^a
• 关键词：D-(TRIS)2SiF6 ; Phase transition ; IR spectra ; Raman spectra ; DFT calculations ; DSC measurements
• 刊名：Vibrational Spectroscopy
• 出版年：2012
• 期刊代码：113_09242031
• 类别：ms
• 出版时间：March, 2012
• 卷：59
• 期：Complete
• 页码：47-58
• 文件大小：2484 K

摘要

[(CH₂OD)₃CND₃]₂SiF₆ ferroic crystal, abbreviated as D-(TRIS)₂SiF₆ crystal was investigated. Optical (linear birefringence) and thermal (differential scanning calorimetry, DSC) measurements indicated a solid-solid phase transition (PT) of the first order at 185 K. The vibrational infrared spectra of powdered D-(TRIS)₂SiF₆ crystal in Nujol and Fluorolube mulls were studied in the wide range of temperature, from 308 K to 133 K. The temperature changes of wavenumber, width, centre of gravity position and intensity of the bands were analyzed to clarify the molecular mechanism of the phase transition and the contribution of SiF₆^{2鈭?/sup> and CH₂OD groups to the PT. A wide range (4000-400 cm鈭?) of internal vibrations of the DTRIS+ and SiF₆2鈭?/sup> ions was investigated and the assignment of the observed infrared absorption bands was discussed. Raman spectra of the crystal at room temperature (RT) were recorded and discussed in relation to the structure of isostructural (TRIS)₂SiF₆ crystal in the range (4000-400 cm鈭?). Theoretical calculations were made based on density functional theory (DFT). The calculated normal vibrational modes of the molecules, their intensities and frequencies were compared with those obtained from experimental data.}