Browsing by Author "Gulebaglan, S. E."

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First-Principles Calculations of Structural and Electronic Properties of Tlxga1-Xas Alloys
(Iop Publishing Ltd, 2016) Akyuz, G. Bilgec; Tunali, A. Y.; Gulebaglan, S. E.; Yurdasan, N. B.
The zincblende ternary alloys TlxGa1-xAs (0 < x < 1) are studied by numerical analysis based on the plane wave pseudopotential method within the density functional theory and the local density approximation. To model the alloys, 16-atom supercells with the 2 x 2 x 2 dimensions are used and the dependency of the lattice parameter, bulk modulus, electronic structure, energy band gap, and optical bowing on the concentration x are analyzed. The results indicate that the ternary TlxGa1-xAs alloys have an average band gap bowing parameter of 4.48 eV for semiconductor alloys and 2.412 eV for semimetals. It is found that the band gap bowing strongly depends on composition and alloying a small Tl content with GaAs produces important modifications in the band structures of the alloys.
First-Principles Investigation of Bowing Parameter in Zinc-Blende Scxga1-Xn
(Taylor & Francis Ltd, 2014) Yurdasan, N. B.; Gulebaglan, S. E.; Tunali, A. Y.; Akyuz, G. B.
We present first-principles calculations of the structural and electronic properties of binary GaN, ScN and [GRAPHICS] alloys in the zinc-blende structure using pseudopotential plane-wave method within the density functional theory. The alloys are described by considering configurations in 16-atom supercells, corresponding to [GRAPHICS] conventional cubic cells. The lattice parameter, bulk modulus, bulk modulus derivation, the energy band gap and bowing parameter are obtained as a function of Sc concentration for ternary alloys [GRAPHICS] . Our studies focus on the concentration dependence of the electronic band structure and bowing parameter of these alloys. We found that [GRAPHICS] composition affects strongly bowing parameter and the band gap increases with increasing Sc concentration for [GRAPHICS] in the zinc-blende structure. The results also show that the energy band gap and bowing parameter of the [GRAPHICS] alloys can be obtained by a third-order polynomial equation, [GRAPHICS] and [GRAPHICS] , respectively.
Theoretical Study of Rhombohedral Nacaf3 Crystal in the Predicted Ferroelectric Phase
(Gazi Univ, 2014) Erdinc, B.; Aycibin, M.; Secuk, M. N.; Gulebaglan, S. E.; Dogan, E. K.; Akkus, H.
The calculated results for structural optimization, electronic band structure, total density of states and optical properties of a rhombohedral NaCaF3 compound were discussed using generalized gradient approximation under the density functional theory. According to our calculation, NaCaF3 crystal has a direct band transition. Moreover, optical properties of NaCaF3 were investigated using scissor approximation. This is the first theoretical study of rhombohedral crystal structure of NaCaF3 as far as we know.