Specific heat of NH4Br and NH4BrxCl1-x crystals close to the antiferroelectric transition

We calculate the specific heat C-VI of NH4Br and mixed crystals of NH4BrxCl1-x using the Ising model for the transition between the disordered (D) and antiferro- (AF) electric phases in these crystalline systems. Our C-VI values, which we calculated for x(Br)=1, 0.26, and 0.51 are in good agreement, both below and above T-C, with the observed C-P data from the literature. Our value of congruent to 0.1 (T < T-C and T>T-C) for the critical exponent of the specific heat agrees with the value of 0.125 predicted by a three-dimensional Ising model.


Excitation intensity- and temperature-dependent photoluminescence in layered structured Tl2GaInSe2S2 crystals
Hasanlı, Nızamı (AIP Publishing, 2013-02-21)
Photoluminescence spectra of Tl2GaInSe2S2 layered crystals have been registered in the temperature range of 17-62 K and in the wavelength region of 525-690 nm. A broad visible photoluminescence band centered at 590 nm (2.10 eV) was observed at T 17 K. Variation of emission band has been studied as a function of laser excitation intensity in the 0.1-55.7 mW cm(-2) range. The analysis of the spectra reveals that the peak energy position changes with excitation intensity (blue shift). The radiative transitions...
Calculation of the Raman frequencies of lattice modes in the disordered phase II of NH4Br at high pressures
Yurtseven, Hasan Hamit (Physics Essays Publication, 2010-01-01)
The Raman frequencies are calculated here at various temperatures for the nu(7) (56 cm(-1)) and nu(5) (134 cm(-1)) lattice modes in the disordered phase II of NH4Br. The lattice parameter data obtained at zero pressure are used to calculate the Raman frequencies of those modes studied for constant pressures of 0.1, 108, and 637.5 MPa in phase II of the NH4Br crystal. Through the mode Gruumlneisen parameter which is kept constant in the disordered phase II, the Raman frequencies calculated decrease linearly ...
Calculation of the infrared frequency and the damping constant (full width at half maximum) for metal organic frameworks
Kurt, M.; Yurtseven, Hasan Hamit; Kurt, Aygül; Aksoy, S. (IOP Publishing, 2019-06-01)
The rho(NH2) infrared (IR) frequencies and the corresponding full width at half maximum (FWHM) values for (CH3)(2)(NH2FeMII)-M-III(HCOO)(6) (DMFeM, M = Ni, Zn, Cu, Fe, and Mg) are analyzed at various temperatures by using the experimental data from the literature. For the analysis of the IR frequencies of the rho(NH2) mode which is associated with the structural phase transitions in those metal structures, the temperature dependence of the mode frequency is assumed as an order parameter and the IR frequenci...
Modelling of non-uniform DC driven glow discharge in argon gas
Rafatov, İsmail; BILIKMEN, S. (Elsevier BV, 2007-07-16)
Physical properties of non-uniform DC-driven glow discharge in argon at pressure 1 torr are analyzed numerically. Spatially two-dimensional axial-symmetric model is based on the diffusion-drift theory of gas discharge. Results presented compare favorably with the classic theory of glow discharges and exhibit good agreement with the experimental result. Comparison with the result of spatially one-dimensional model is performed. (c) 2007 Elsevier B.V. All fights reserved.
Trap distribution in TlInS2 layered crystals from thermally stimulated current measurements
IŞIK, MEHMET; Goksen, K.; Hasanlı, Nızamı; Ozkan, H. (Korean Physical Society, 2008-02-01)
We have carried out thermally stimulated current (TSC) measurements with the current flowing along the layer on as-grown TlInS2 layered single crystals in the low temperature range 10 - 110 K with different heating rates of 0.1 - 1.5 K/s. Experimental evidence was found for the presence of two shallow electron trapping centers with activation energies of 12 and 14 meV. Their capture cross sections have been determined as 2.2 x 10(-23) and 7.1 x 10(-25) cm(2), respectively. It was concluded that retrapping i...
Citation Formats
H. H. Yurtseven, “Specific heat of NH4Br and NH4BrxCl1-x crystals close to the antiferroelectric transition,” JOURNAL OF APPLIED PHYSICS, pp. 0–0, 2005, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/40924.