Vibrational Spectroscopic Properties of a [C(NH2)3]4Cl2SO4 Ferroelectric Crystal - An Experimental and Theoretical Study |
| D. Podsiadłaa, O. Czupińskib, D. Dudzicc and Z. Czaplad,a
aInstitute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław, Poland bFaculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland cInstitute of Low Temperature and Structure Research of the Polish Academy of Sciences, Okólna 2, 50-422 Wrocław, Poland dDepartment of Physics, Opole University of Technology, Ozimska 75, 45-271 Opole, Poland |
| Received: August 30, 2013; In final form: November 22, 2013 |
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| Tetraguanidinium dichloride-sulphate crystal, [C(NH2)3]4Cl2SO4, abbreviated as G4Cl2SO4 was investigated. The vibrational infrared spectra of powdered G4Cl2SO4 crystal in Nujol mull were studied in the wide range of temperature, from 298 K to 377 K. This temperature range contains all the phases in the crystal (named III, II, I on heating, respectively). The temperature changes of wavenumbers, centre of gravity, and intensity of the bands were analyzed to clarify the molecular mechanism of the phase transitions. It was shown that in cooling from 377 K to 313 K the phase II is the same as the room temperature phase. Information about hydrogen bonds was obtained. The time dependence of internal vibrations at 356 K was observed and it was connected with slow transition III → II. For more detailed band assignment Raman spectrum at room temperature, at ferroelectric phase was carried out. Theoretical calculations were made based on density functional theory, with the B3LYP method using 6-311 + G(d,p) basic set. Calculated normal vibrational modes of the molecule, their frequencies and intensities were compared with these recorded in experiment. Theoretical description of the molecule including hydrogen bonds were optimized and the bond parameters were obtained. The Mulliken charges population analysis was performed. |
DOI: 10.12693/APhysPolA.125.115 PACS numbers: 78.30.-j, 78.20.Bh, 77.80.B- |