Browsing by Author "Erzen, Mehmet"

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Comprehensive Theoretical Investigation of Electronic, Structural, Optical, Elastic, and Thermodynamic Properties of Orthorhombic Srta2o6 Compound
(Canadian Science Publishing, 2022) Erzen, Mehmet; Aycibin, Murat; Akkus, Harun
The structural, optical, dynamic, elastic, and thermodynamical properties of orthorhombic SrTa2O6 were computed using density functional theory via two computation codes, namely Wien2k and ABINIT. The findings reveal that SrTa2O6 is a wide bandgap semiconductor with 4.6 eV using the TB-mBJ approximation. The results of bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy factors, and Debye's temperature were obtained and discussed in detail. Moreover, The ductile behavior and structural stability mechanism were also explained.
Computation of Physical Properties of Ferroelectric Rbnbo3 Under Pressure
(Taylor & Francis Ltd, 2018) Erzen, Mehmet; Akkus, Harun
The electronic, linear optic and elastic properties of RbNbO3 crystal have been calculated under pressure using the density functional theory for its five different phases, P-1, Pm-3m, P4mm, Amm2 and R3m. It is shown that RbNbO3 crystal electrically exhibits a semiconductor property under zero pressure in these phases except for triclinic phase, P-1, in which the compound has insulator property. Also, the crystal has a direct band gap in the Amm2 phase while it has an indirect band gap in the other four phases. Moreover, the electronic properties were calculated under pressure and it is shown that the locations of top of the valence band and the bottom of the conduction band in the Brillouin Zone were varied with the effect of pressure. The linear optical functions such as dielectric function, refractive index, absorption and extinction coefficients depend on light frequency were calculated under various pressure values for all phases and it is shown that values of the optical constants change with the effect of pressure. Finally, the elastic stiffness tensor of RbNbO3 were calculated for four phases, Pm-3m, P4mm, Amm2 and R3m and the variations of some elastic constants, such as Debye temperature, Poisson ratio, bulk modulus, shear modulus, and Young modulus, with the pressure were investigated.
Effect of Pressure on Physical Properties of Luaso4 Crystal
(Iop Publishing Ltd, 2018) Erzen, Mehmet; Akkus, Harun
The physical properties of LuAsO4, such as structural, electronic, linear optical, dynamic, and thermodynamic properties, have been studied under pressure using the density functional theory within the local density approximation. The calculations of electronic band structure of the crystal show that it is an insulator with an indirect band gap value of 4.1977 eV at zero pressure and that the value of band gap increase by increasing pressure. The linear optical properties of the crystal, dependent on the frequency of incoming light, have been calculated. The components of dielectric tensor, static dielectric constant, and refractive index have been calculated under pressure while some optical constants such as energy loss function, extinction coefficient, absorption coefficient, reflectivity, effective dielectric constant, and effective number of valence electrons have been calculated at zero pressure. Moreover, the phonon dispersion, some thermodynamic potentials such as free energy, internal energy, and some thermodynamic properties such as entropy and heat capacity have been calculated under pressure.
Exploring Electronic, Structural, Optical, and Elastic Properties of Mgx2o6 (X = Ta, Nb) Compounds for Photovoltaic and Optoelectronic Applications: First Study Effort
(indian Assoc Cultivation Science, 2024) Aycibin, Murat; Celebi, Mustafa; Erzen, Mehmet; Akkus, Harun
In this study, the structural, optical, and elastic properties of tetragonal MgTa2O6 and orthorhombic MgNb2O6 were determined using the Wien2k and ABINIT computational programs with the aid of density functional theory. The results imply that both compounds are classified as wide band gap semiconductor with 4.143 eV (for MgTa2O6) and 3.653 eV (for MgNb2O6) with PBEsol-GGA + TB-mBJ approximation. The findings of bulk modulus, shear modulus, Young modulus, Poisson's ratio, and anisotropy factors were determined and discussed in detail. The ductile behavior and the mechanism of structural stability were also explained.
Nbsbo4 Kristalinin Yapısal, Elastik ve Piezoelektrik Özelliklerinin İncelenmesi
(2023) Erzen, Mehmet
NbSbO4 kristalinin yapısal, elastik ve piezoelektrik özellikleri, yoğunluk fonksiyonel teorisine dayalı olarak hesaplandı. Bu özellikler için hesaplamalar hem genelleştirilmiş gradyent hem de yerel yoğunluk yaklaşımı altında ABINIT paket programı kullanılarak yapılmıştır. NbSbO4 kristali için elastik sertlik tensörü ve elastik uyum tensörü, temel durumda hesaplanmıştır. Elastik sertlik ve elastik uyum tensörü kullanılarak NbSbO4 kristali için Voigt Bulk Modülü, Reuss Bulk Modülü, Hill Bulk Modülü, Voigt Shear Modülü, Reuss Shear Modülü, Hill Shear Modülü, Young Modülü, Poisson Oranı, Esneklik Katsayısı, Debye sıcaklığı, boyuna ses dalgası hızı, enine ses dalgası hızı ve ortalama ses hızı hesaplanmıştır. Daha sonra NbSbO4 kristalinin temel durumda piezoelektrik tensörü hesaplandı. Buna bağlı olarak, MTEX yazılımı kullanılarak piezoelektrik tensörünün 2 boyutta boyuna yüzeyleri ve 3 boyutta temsil yüzeyleri elde edilmiştir. Hem genelleştirilmiş gradyent yaklaşımı hem de yerel yoğunluk yaklaşımları ile elde edilen özellikler karşılaştırılmıştır. Yapılan hesaplamalar sonucunda malzemenin her iki yaklaşım için de esnek ve şekillendirilebilir bir malzeme olduğu anlaşılmıştır.
Piezoelektrik Zr3geo8 Kristalinin Fiziksel Özellikleri
(2023) Erzen, Mehmet
Yoğunluk fonksiyonel teorisine ve ilk temel hesaplamalara dayanarak, Zr3GeO8 kristalinin temel durum için fiziksel özellikleri hesaplanmıştır. Yapılan tüm hesaplamalarda Yoğunluk fonksiyonel teorisi tabanlı çalışan ABINIT paket programı kullanılmıştır. İncelemeler yerel yoğunluk yaklaşımı altında yapılmıştır. Zr3GeO8 kristalinin geometrik optimizasyonu, valans elektronlarının durum yoğunluğu, kristalin iletkenlik karakterini anlamak için elektronik bant yapısı, malzemenin elektromanyetik dalgaya tepkisini görmek için doğrusal optik özellikleri hesaplanmıştır. Ayrıca Zr3GeO8 kristali için dinamik-termodinamik özellikleri hesaplanmıştır. Hesaplanan yapısal optimizasyon ve elektronik bant yapısına göre Zr3GeO8 kristalinin bant aralığı 4.4663 eV olup dolaylı bir bant aralığına sahip olduğu elde edilmiştir. Zr3GeO8 kristali için temel durumdaki lineer optik özellikler ve lineer optik özelliklere bağlı olarak enerji kaybı fonksiyonları, yansıtma ve absorpsiyon katsayısı gibi bazı sabitler hesaplanır. Zr3GeO8 kristalinin fonon dağılımı, durum yoğunluğu ve her bir atomun durum yoğunluğuna katkısı hesaplandı. Son olarak Zr3GeO8 kristali için serbest enerji, iç enerji, entropi ve ısı kapasitesi hesaplanmıştır.
Theoretical Prediction by Dft on Properties of ??-Srta2o6 Crystal
(Univ Novi Sad, Fac Technology, 2023) Aycibin, Murat; Erzen, Mehmet; Akkus, Harun
Based on the Density Functional Theory (DFT) electronic band structure, state density, linear optics, elastic, dynamic and thermodynamic properties of /3 '-SrTa2O6 crystal with P4/mbm (No. 127) space group were in-vestigated with the help of ABINIT and Wien2k code. In the study, it was found that the /3 '-SrTa2O6 crystal is classified as a semiconductor with an indirect bandgap. For this crystal, the dielectric function was obtained and optical constants such as energy loss function, extinction coefficient, absorption coefficient and reflectivity were calculated. The components of the elastic stiffness tensor, the phonon dispersion, the state density and the contribution of each atom to the state density were obtained. Finally, thermodynamic properties were deter-mined for the /3 '-SrTa2O6 crystal. Furthermore, the changes in free energy (F), internal energy (E), entropy (S) and heat capacity (C) depending on the temperature were investigated.
Thermally Switchable Terahertz Absorber Based on a Vo2-Included One-Dimensional Photonic Crystal
(Springer Heidelberg, 2023) Roumi, Bita; Erzen, Mehmet; Abdi-Ghaleh, Reza; Akkus, Harun; Zhou, Yuanguo; Prajapati, Yogendra Kumar; Maurya, Jitendra Bahadur
Here, a thermally switching absorber based on a one-dimensional photonic crystal containing a phase change material is proposed, which operates in the terahertz range. Vanadium dioxide (VO2) is utilized as the phase-change material in the structure, which shows semiconductor-to-metal transition with varying temperatures. The frequency of switching is regulated in such a way that according to the VO2 thickness, the absorption band displays switching properties from low to high frequencies and vice versa, and also from narrow to broadband absorption at the same frequency when the temperature increases from 300 to 350 K. The absorptivity in both bands is obtained at over 90%. Field distribution profile and the impedance matching technique elucidate the physical mechanism of absorption peaks. At 300 K, maximum absorption is realized by localizing the intensity at the defect layer, and at 350 K, the Tamm state excitation makes it possible to achieve perfect absorption. Also, relative impedance matching of the structure at the peak frequencies with vacuum impedance explains high absorption. Finally, the effects of incidence angle and polarization of light that influence the absorption peaks are analyzed. According to the results, the proposed absorber, despite showing switching features between two bands, also can be adjusted by incident angle for both TE and TM polarizations. This work may have potential applications in designing terahertz switches, filters, and sensors.