Browsing by Author "Gulebaglan, S. Erden"

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The Composition Effect on The Bowing Parameter in The Cubic Tlxal1-Xas
(World Scientific Publ Co Pte Ltd, 2012) Gulebaglan, S. Erden
The band gap bowing parameter of the new semiconductor TlxAl1-xAs alloys are investigated numerically based on first-principles calculations and the local density approximation. A 16-atom supercell is used to model for the ternary TlxAl1-xAs alloys. The alloy's lattice constants obey Vegard's law well. Band gap bowing coefficients show very strong composition dependence. The results suggest that the unstrained band gap bowing parameter of the ternary TlxAl1-xAs alloys is b = 1.9754 eV. The results also suggest that the composition-dependent band gap energy of the zincblende alloys can be expressed by a third-order polynomial equation, E-g(x) = -7.2064x(3) + 14.8397x(2) - 10.016x + 2.2217 eV.
Structural and Electronic Properties of Gaxtl1-Xp Ternary Alloys
(Elsevier Sci Ltd, 2015) Tunali, A. Yildiz; Gulebaglan, S. Erden; Yurdasan, N. Boz; Akyuz, G. Bilgec
The structural and electronic properties of GaxTl1-xP ternary alloys in zincblende phase were studied using pseudopotential plane wave method within the density functional theory. The dependence of the lattice parameter, bulk modulus, its pressure derivative, electronic structure, energy band gap and optical bowing on the composition x were analyzed for 0 < x < 1 with small increments, disregarding the so long computational time. The lattice parameters were optimized exhibiting linear concentration dependence in accordance with Vegard's law. The bulk modulus as a function of gallium composition shows linear-like concentration dependence with a large upward bowing parameter equal to 10.79 GPa. We found that the band gap increases with increasing compositions of Ga, so that the compounds change from metal to semiconducting phase and could be useful for device applications in spintronics, especially at certain contributions. As a consequence the band gap bowing is found to be strongly composition dependent. The microscopic origins of the gap bowing were detailed and explained according to Zunger approach. (C) 2015 Elsevier Ltd. All rights reserved.
Structural, Electronic, Dynamic, Optic and Elastic Properties of Mgscga Via Density Functional Theory
(Pergamon-elsevier Science Ltd, 2021) Dogan, E. Kilit; Gulebaglan, S. Erden
The structural, electronic and phonon properties of the MgScGa compound were investigated by density functional theory using the generalized gradient approximation. Some basic structural properties of this compound, such as the lattice constants, bulk modulus and pressure derivative of the bulk module have been studied. Electronic properties were investigated by calculating and analyzing the electronic band structure and total density of states graphs for the MgScGa compound. Electronic band structure calculations showed that MgScGa compound has a semiconductor structure. Phonon spectra were calculated using a linear response method within the framework of the total predicted state density, density functional perturbation theory for the MgScGa compound. A factor group analysis has been performed in order to get the decomposition of whole representation of Gamma of MgScGa compound into irreducible representation. For investigation of optic properties; real and imaginary components of complex dielectric function, reflectivity (R), refractive index (n), extinction coefficients (k), energy-loss functions for volume (L-V) and surface (L-S), the effective number of valence electrons per unit cell (N-eff) were calculated. Elastic properties are revealed by calculating the elastic stiffness constants, Bulk, Shear and Young modulus, Poisson Ratio, Flexibility Coefficient and Zener anisotropy constant.
Structural, Thermodynamic and Phonon Properties of Sbsi and Sbsbr Single Crystals
(Korean Physical Soc, 2013) Dogan, E. Kilit; Aycibin, M.; Gulebaglan, S. Erden; Secuk, M. N.; Erdinc, B.; Akkus, H.
The structural, dynamical and thermodynamic properties of antimony sulfoiodide (SbSI) and antimony sulfobromide (SbSBr) are investigated by using an ab-initio pseudopotential method applying density functional theory (DFT) within the local density approximation (LDA). The dynamical properties, such as the phonon dispersion and the phonon density of states, are calculated. Making a factor group analysis we classify the phonon modes. Moreover, the thermodynamic properties, such as the entropy and the constant-volume specific heat, as functions of temperature and the phonon contribution to the free energy and the internal energy are calculated.