Yazar "Koc, H." seçeneğine göre listele

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    Ab initio Modeling of Elastic and Optical Properties of Sb and Bi Sesquioxides
    (Iop Publishing Ltd, 2018) Koc, H.; Akhundov, Chingiz G.; Mamedov, Amirullah M.; Ozbay, Ekmel
    First-principle calculations performed the structural, mechanical, electronic, and optical properties of Sb2O3 and Bi2O3 compounds in monoclinic (claudetite and alpha-Bi2O3) and orthorhombic (valentinite) structures. Local density approximation has been used for modeling exchange-correlation effects. The lattice parameters, bulk modulus, and the first derivate of bulk modulus (to fit to the Murnaghan's equation of state) of considered compounds have been calculated. The second-order elastic constants have been calculated, and the other related quantities have also been estimated in the present work. The electronic bands structures and the partial densities of states corresponding to the band structures are presented and analyzed. The real and imaginary parts of dielectric functions and energy-loss function are calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.
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    Electron Spectroscopy and the Electronic Structure of KNbO3: First Principle Calculations
    (Taylor & Francis Ltd, 2014) Simsek, S.; Koc, H.; Trepakov, V. A.; Mamedov, A. M.; Ozbay, E.
    The electronic structures of KNbO(3)were calculated within the density functional theory, and their evolution was analyzed as the crystal-field symmetry changes from cubic to rhombohedral via tetragonal phase. We carried out electron-energy loss spectroscopy experiments by using synchrotron radiation and compared the results with the theoretical spectra calculated within Density Functional Theory. The dominant role of the NbO(6)octahedra in the formation of the energy spectra of KNbO(3)compound was demonstrated. The anomalous behavior of plasmons in ferroelectrics was exhibited by the function representing the characteristic energy loss in the region of phase transition.
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    First principles prediction of the elastic, electronic, and optical properties of Sb2S3 and Sb2Se3 compounds
    (Elsevier, 2012) Koc, H.; Mamedov, Amirullah M.; Deligoz, E.; Ozisik, H.
    We have performed a first principles study of structural, mechanical, electronic, and optical properties of orthorhombic Sb2S3 and Sb2Se3 compounds using the density functional theory within the local density approximation. The lattice parameters, bulk modulus, and its pressure derivatives of these compounds have been obtained. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, Debye temperature, and hardness have also been estimated in the present work. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valence electrons and the effective optical dielectric constant are calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data. (C) 2012 Elsevier Masson SAS. All rights reserved.
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    First-principles study of the structural, elastic, electronic, optical, and vibrational properties of intermetallic Pd 2Ga
    (2012) Yildirim, A.; Koc, H.; Deligoz, E.
    The structural, elastic, electronic, optical, and vibrational properties of the orthorhombic Pd 2Ga compound are investigated using the norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters have been compared with the experimental values and found to be in good agreement with these results. The second-order elastic constants and the other relevant quantities, such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocity, and Debye temperature, have been calculated. It is shown that this compound is mechanically stable after analysing the calculated elastic constants. Furthermore, the real and imaginary parts of the dielectric function and the optical constants, such as the optical dielectric constant and the effective number of electrons per unit cell, are calculated and presented. The phonon dispersion curves are derived using the direct method. The present results demonstrate that this compound is dynamically stable. © 2012 Chinese Physical Society and IOP Publishing Ltd.
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    Optical Properties and Electronic Band Structure of Topological Insulators (on A25B36 Compound Based)
    (Taylor & Francis Ltd, 2013) Koc, H.; Mamedov, Amirullah M.; Ozbay, Ekmel
    We have performed a first principles study of structural, electronic, and optical properties of rhombohedral Sb2Te3 and Bi2Te3 compounds using the density functional theory within the local density approximation. The lattice parameters, bulk modulus, and its pressure derivatives of these compounds have been obtained. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valance electrons and the effective optical dielectric constant are calculated and presented in the study.
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    The elastic, electronic, and optical properties of PtSi and PtGe compounds
    (Taylor & Francis Ltd, 2011) Koc, H.; Deligoz, E.; Mamedov, Amirullah M.
    The structural, mechanical, electronic and optical properties of orthorhombic PtSi and PtGe were investigated using norm-conserving pseudopotentials within the local density approximation in the frame of density functional theory. The calculated lattice parameters and bulk modulus for PtSi and PtGe have been compared with the experimental and theoretical values. The second-order elastic constants were calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities and Debye temperature have also been estimated. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valance electrons and the effective optical dielectric constant were calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.