Thermal Expansivity Related to the Frequency Shifts for the I-II Phase Transition In Ammonium Iodide

We calculate here the temperature dependence of the frequency shifts (1/v)/(partial derivative v/partial derivative P)(T) for the v (125 cm(-1)) Raman mode of NH(4)I close to the I-II phase transition (T(c)=257 K). For this calculation the lattice parameter data for NH(4)I is used. We establish the Pippard relation in terms of the spectroscopic parameters by correlating the thermal expansivity alpha(P) with the frequency shifts (1/v)/(partial derivative v/partial derivative P)(T) through the mode Gruneisen parameter of the v (125 cm(-1)) mode for the I-II phase transition in NH(4)I. From a linear variation of alpha(P) with the (1/v)/(partial derivative v/partial derivative P)(T) for the v (125 cm(-1)) Raman mode according to the Pippard relation, we extract the slope value of dP/dT=18.9 bar/K, which agrees with the observed value for the I-II phase transition in a P-T phase diagram of NH(4)I.
2nd International Conference on Perspectives in Vibrational Spectroscopy


Temperature Dependence of The Raman Frequency Shifts Related to The Specific Heat and Thermal Expansion Close To I-II Phase Transition in S-Triazine.
KURT, MUSTAFA; Yurtseven, Hasan Hamit (Walter de Gruyter GmbH, 2010-01-01)
A linear variation of the specific heat C-p with the frequency shifts 1/omega(partial derivative omega/partial derivative T)(p) is established for the Raman modes I-V at various temperatures (P=0) close to I-II phase transition in s-triazine (T-c=198 K).
Temperature dependence of the Raman frequencies and bandwidths close to phase transitions in ammonium halides
Yurtseven, Hasan Hamit (2001-09-01)
In this study, we give the temperature dependence of our observed frequencies and bandwidths for the Raman optical modes in the ammonium halides close to the phase transitions of the first order (NH4 Br), tricritical (NH4Cl) and second order (NH4Cl). Using the predictions of an [sing pseudospin-phonon coupled model, which considers interactions between two spin and two phonons, our observed Raman data have been interpreted qualitatively. Our results show that an Ising model considered here can explain the o...
Critical behaviour of the specific heat calculated using the Raman frequencies of the lattice and internal modes near the lambda-phase transition in NH4Br
Sen, S.; Yurtseven, Hasan Hamit (Elsevier BV, 2007-05-27)
We calculate here the specific heat of NH4Br using our Raman frequency shifts for the lattice mode Of nu(7) TA (56 cm(-1)) and the internal mode Of nu(2) (1684 cm(-1)) near its lambda-phase transition (T-lambda = 234 K, P = 0). By analyzing our Raman frequency shifts, values of alpha = 0. 19 (T < T-lambda, and T > T-lambda) for the lattice mode, and alpha = 0.45 (T < T-lambda) and alpha = 0.57 (T > T-lambda) for the internal mode, are used as the values of the critical exponent for the specific heat to pred...
Raman frequencies calculated as functions of temperature and pressure using volume data for solid phase I of benzene
Yurtseven, Hasan Hamit (2017-01-01)
Raman frequencies of six lattice modes are calculated as a function of pressure using the volume data from the literature by means of the isothermal mode Gruneisen parameter (gamma(T)) for the solid phase I of benzene. We find that by determining the yr decreasing, the Raman frequencies calculated for the phonon modes increase with increasing pressure in this solid phase of benzene, which agree with the observed Raman data. We also predict the T-P phase diagram between the solid phases of I and I' by using ...
Temperature dependence of the polarization, dielectric constant, damping constant and the relaxation time close to the ferroelectric-paraelectric phase transition in LiNbO3
Kiraci, A.; Yurtseven, Hasan Hamit (2017-01-01)
We calculate the order parameter (spontaneous polarization) and the inverse dielectric susceptibility at various temperatures in the ferroelectric phase of LiNbO3 for its ferroelectric-paraelectric phase transition (T-C =1260 K) using the Landau phenomenological model. For this calculation, the Raman frequencies of the soft optic mode (TO1) are used as the order parameter and the fitting procedure is employed for both the order parameter and the inverse dielectric susceptibility by means of the observed dat...
Citation Formats
H. H. Yurtseven, “Thermal Expansivity Related to the Frequency Shifts for the I-II Phase Transition In Ammonium Iodide,” Mar Ivanios Coll, Thiruvananthapuram, India, 2008, vol. 1075, Accessed: 00, 2020. [Online]. Available: