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Analysis of vibrational spectra in relation to the thermodynamic quantities close to the phase transitions in ammonium halides (NH4F and NH4I)
Date
2017-01-01
Author
Tari, O.
Yurtseven, Hasan Hamit
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The pressure dependences of the vibrational frequencies of the TO and L modes are analyzed from the literature data and the thermodynamic quantities such as isothermal compressibility K gamma, thermal expansion alpha p and the specific heat C-p - C-v are calculated through the mode Grilneisen parameters of those modes in ammonium halides (NH4F and NH4I). For this calculation, the observed frequencies of the TO mode (238 cm(-1) at 1 bar) and the L mode (74.7 meV at 1.9 GPa) are used for the phases of I, II and III in NH4F, whereas for the phases of V and VI in NH4F, the observed frequencies of the 238 cm(-1) are used as a function of pressure at T=293 K. We also analyze the observed frequencies for the TO (17.1 meV) and L (34.1 meV) modes (P=0, T=-25 degrees C) in the phase II of NH4I and the thermodynamic quantities (K-T, alpha(p) and C-p - C-v) are calculated as a function of pressure (T=-25 degrees C) through the mode Gruneisen parameters of the TO and L modes in phase II of NH(4)l.
Subject Keywords
NH4F and NH4I
,
Thermodynamic quantities
,
TO and L modes
,
Vibrational spectra
URI
https://hdl.handle.net/11511/41972
Journal
OPTIK
DOI
https://doi.org/10.1016/j.ijleo.2017.01.107
Collections
Department of Physics, Article
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O. Tari and H. H. Yurtseven, “Analysis of vibrational spectra in relation to the thermodynamic quantities close to the phase transitions in ammonium halides (NH4F and NH4I),”
OPTIK
, pp. 244–251, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41972.