Yazar "Kurt, A." seçeneğine göre listele

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    Öğe
    Calculation of the infrared frequency and the damping constant (full width at half maximum) for metal organic frameworks
    (Iop Publishing Ltd, 2019) Kurt, M.; Yurtseven, H.; Kurt, A.; Aksoy, S.
    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 frequencies are calculated by using the molecular field theory. Also, the temperature dependence of the IR frequencies and of the damping constant as calculated from the models of pseudospin (dynamic disorder of dimethylammonium (DMA(+)) cations)-phonon coupling (PS) and of the energy fluctuation (EF), is fitted to the observed data for the wavenumber and FWHM of the rho(NH2) IR mode of the niccolites studied here. We find that the observed behavior of the IR frequencies and the FWHM of this mode can be described adequately by the models studied for the crystalline structures of interest. This method of calculating the frequencies (IR and Raman) and FWHM of modes which are responsible for the phase transitions can also be applied to some other metal organic frameworks.
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    Öğe
    Calculation of the Raman and IR frequencies as order parameters and the damping constant (FWHM) close to phase transitions in methylhydrazinium structures
    (Elsevier Science Bv, 2019) Kurt, M.; Yurtseven, H.; Kurt, A.
    Temperature dependences of the frequencies for the Raman modes of v (NH2), v(s) (CH3), v(1) (HCOO-), vs (CNN) and IR mode of rho (NH2) are calculated in particular, for MHyMn close to the phase transition temperature (T-C = 220 K) in the family of compounds CH3NH2NH2 M(HCOO)(3), MHyM with M = Mn, Mg, Fe and Zn. By assuming Raman and infrared frequency as an order parameter, this calculation is performed from the molecular field theory by using the experimental data from the literature. We also calculate the damping constant (FWHM) from the order parameter (Raman and IR frequency of those modes) by using the pseudospin (MHy(+) cations)-phonon coupled model (PS) and the energy-fluctuation model (EF) for methylhydrazinium metal formate frameworks. Expressions of the damping constant from both models are fitted to the observed FWHM data for the Raman and infrared modes studied for these metal formates. Our results show that the anomalous behaviour of the Raman and IR frequencies of those modes, except the v(S)(CH3) Raman mode which are associated with the phase transition can be described adequately by the molecular field theory in MHyM, as observed experimentally. Also, the damping constant calculated from the PS and EF models can explain the observed FWHM of those Raman and IR modes studied in methylhydrazinium metal formate frameworks. (C) 2019 Elsevier B.V. All rights reserved.
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    Öğe
    Effects of viscosity on the behavior of entropy change in the shock wave that occurred after the December 13, 2006 coronal mass ejection
    (Maik Nauka/Interperiodica/Springer, 2015) Cavus, H.; Kurt, A.
    Coronal mass ejections (CMEs) and the solar wind are the two main demonstrations of solar activity. These events can drive a shock wave. The shock wave occurs where the solar wind changes from being supersonic (with respect to the surrounding interplanetary medium) to subsonic. The main purpose of this study is to apply the algorithm and the results given in our recent papers to the shock wave that happened after the December 13, 2006 CME, and evaluate the behavior of entropy during this solar activity.