Browsing by Author "Gulebaglan, Sinem Erden"

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Ab Initio Calculations of Structural, Electronic, Elastic, Optical, and Dynamical Properties of Half-Heusler Lisib Compound
(Springer, 2022) Akyuz, Gonul Bilgec; Dogan, Emel Kilit; Yurdasan, Nazli Boz; Tunali, Aylin Yildiz; Gulebaglan, Sinem Erden
Structural, electrical, elastic, optical, and dynamical properties of LiSiB half-Heusler compound were analyzed based on density functional theory implemented in Quantum Espresso and ABINIT package programs. The effects of exchange-correlation interactions are handled by the generalized gradient approximation with Perdew-Burke-Ernzerhof parametrization. Firstly, the structure of this half-Heusler compound has been optimized and our results indicate that LiSiB reveals semiconducting behavior with an indirect band gap of 0.21 eV. The elastic constants, and other elastic modules have been computed. The mechanical stabilities of these alloys have been theoretically confirmed. The phonon dispersion spectra and phonon density of states in the Brillouin zone have been obtained and discussed. Also, the optical properties were calculated, and the results showed that the LiSiB alloy has a strong optical transition and the LiSiB crystal could be used in the design of optoelectronic devices. There are no results found on elastic, optical, and phonon features of LiSiB in the literature; hence, the findings reported here shed light on future studies.
Calculation of Electronic Band Structure of Ferroelectric Semiconductor Bismuth Niobium Oxyfluoride (Bi2nbo5f) Crystal
(Gazi Univ, 2014) Erdinc, Bahattin; McCabe, Emma; Duran, Duygu; Secuk, M. Nurullah; Gulebaglan, Sinem Erden; Dogan, Emel Kilit; Akkus, Harun
In this study, the geometric structural optimization, electronic band structure and density of states ( DOS) for electrons of ferroelectric Bi2NbO5F structure with space group Pca21 have been investigated using the density functional theory (DFT) under the local density approximation (LDA). The ground state properties of ferroelectric Bi2NbO5F structure are studied. The computed ground state properties and experimental results are consistent. The energy band structure of Bi2NbO5F compound below T-c shows that it is a ferroelectric semiconductor with narrow band gap of 0.0589 eV. Unfortunately, there is neither experimental nor theoretical electronic band structure study of Bi2NbO5F crystal in the literature, so we could not compare our results.
The Calculation of Some Gamma Shielding Parameters for Semiconductor Cspbbr3
(Amer inst Physics, 2017) Oto, Berna; Gulebaglan, Sinem Erden; Kanberoglu, Gulsah Saydan
Recently, researchers produced perovskites structures used in optoelectronic devices as substrates, sensors. CsPbBr3 crystal is found in the cubic perovskite structure and its space group is Pm-3m. CsPbBr3 is a developing material for detection of X- and gamma-ray radiations and the knowledge of the attenuation parameters of CsPbBr3 crystal is important. In this study, some photon shielding parameters such as mass attenuation coefficient (mu(p)), effective atomic number (Z(eff)), and electron density (N-el) have been investigated for CsPbBr3 compound. The theoretical values of mu(p) have been calculated in the energy range from 1 keV to 100 GeV using WinXCom computer code and these values have been used in order to calculate the values of Z(eff) and N-el in the same energy range.
A Comparison Study of the Structural Electronic, Elastic and Lattice Dynamic Properties of Zrinau and Zrsnpt
(Walter de Gruyter Gmbh, 2021) Gulebaglan, Sinem Erden; Dogan, Emel Kilit
To estimate the structural, electronic, elastic and dynamic properties of ZrInAu and ZrSnPt compounds, the density functional theory within the general gradient approximation was used. The computed lattice parameters, bulk modulus and the derivation of bulk modulus with respect to pressure were displayed and compared with the theoretical result. The indirect band gap for ZrInAu was found to be 0.48 eV, and for ZrSnPt the indirect band gap was found as 1.01 eV. Elastic stiffness constants, bulk, shear and Young's module, Poisson's coefficients and Zener anisotropy factor are calculated. Elastic properties showed that the ZrSnPt compound is more durable than the ZrInAu compound. Phonon distribution curves and density of states were investigated using a density functional perturbation theory. Both ZrInAu and ZrSnPt compounds were demonstrated to be dynamically stable. The results of this study were obtained for the first time in the literature. These results will make an important contribution to the literature.
A Computational Estimation on Structural, Electronic, Elastic, Optic and Dynamic Properties of Li2tla (A=sb and Bi): First-Principles Calculations
(Elsevier Sci Ltd, 2022) Dogan, Emel Kilit; Gulebaglan, Sinem Erden
The structural, electronic, optic, elastic and dynamic properties of Li2TlSb and Li2TlBi full-Heusler structure are studied by first principles calculations. The plane wave pseudo-potential method with a generalized gradient approximation was used to calculate all these properties. Quantum Espresso program was used to examine structural, electronic and dynamic properties, and Abinit program was used to examine optical and elastic properties. The change correlation function chosen is the Perdew - Burke - Ernzerhof function. The currently calculated structural properties are in good agreement with other theoretical results. Based on the linear harmony of the stress-strain relationship, the elastic constants of these structures have been determined. Poisson's coefficients and Zener anisotropy factor, Bulk, Shear and Young Module are computed. With the density functional perturbation theory, the frequencies of the phonon distribution spectra throughout the entire brillouin region were calculated and all values were found to be positive. These results show that the dynamic stabilities of Li2TlBi and Li2TlSb crystals are strong. The results obtained in this study are thought to be useful in future scientific studies to explore the applications of these materials such as optoelectronic devices and sensors.
The Dip Effect Under Integer Quantized Hall Conditions
(Springer, 2014) Gulebaglan, Sinem Erden; Kalkan, Sirri Batuhan; Sirt, Serkan; Kendirlik, Enver Metin; Siddiki, Afif
In this work we investigate an unusual transport phenomenon observed in two-dimensional electron gas under integer quantum Hall effect conditions. Our calculations are based on the screening theory, using a semi-analytical model. The transport anomalies are dip and overshoot effects, where the Hall resistance decreases (or increases) unexpectedly at the quantized resistance plateaus intervals. We report on our numerical findings of the dip effect in the Hall resistance, considering GaAs/AlGaAs heterostructures in which we investigated the effect under different experimental conditions. We show that, similar to overshoot, the amplitude of the dip effect is strongly influenced by the edge reconstruction due to electrostatics. It is observed that the steep potential variation close to the physical boundaries of the sample results in narrower incompressible strips, hence, the experimental observation of the dip effect is limited by the properties of these current carrying strips. By performing standard Hall resistance measurements on gate defined narrow samples, we demonstrate that the predictions of the screening theory is in well agreement with our experimental findings.
The Effect of Disorder on Local Electron Temperature in Quantum Hall Systems
(Springer, 2021) Yurdasan, Nazli Boz; Gulebaglan, Sinem Erden; Siddiki, Afif
The local electron temperature distribution is calculated considering a two dimensional electron system in the integer quantum Hall regime in presence of disorder and uniform perpendicular magnetic fields. We solve thermo-hydrodynamic equations to obtain the spatial distribution of the local electron temperature in the linear-response regime. It is observed that, the variations of electron temperature exhibit an antisymmetry regarding the center of the sample in accordance with the location of incompressible strips. To understand the effect of sample mobility on the local electron temperature we impose a disorder potential calculated within the screening theory. Here, long range potential fluctuations are assumed to simulate cumulative disorder potential depending on the impurity atoms. We observe that the local electron temperature strongly depends on the number of impurities in narrow samples.Graphic abstractThe electron temperature Te versus position calculated for different values of the modulation potential V0. The calculations are done at TL=0.04EF0/kB lattice temperature considering impurity Nl=6600 and repeated for three different values of magnetic field omega c/EF0=0.80, 0.85 and 0.90. The insets show the enlarged region for the left side.
Effective Atomic Numbers, Electron Densities and Gamma Rays Buildup Factors of Inorganic Metal Halide Cubic Perovskites Csbx3 (B = Sn, Ge; X = I, Br, Cl)
(Pergamon-elsevier Science Ltd, 2019) Oto, Berna; Gulebaglan, Sinem Erden; Madak, Zekiye; Kavaz, Esra
The present investigation has been undertaken to evaluate gamma radiation shielding effectiveness of inorganic metal halide cubic perovskites CsBX3 (B = Sn, Ge, Pb; X = I, Br, Cl). The values of mass attenuation coefficients (mu/rho) were computed at the energy range of 1.00 keV-100 GeV by WinXCom computer code. Thereupon, half value layer (HVL), the effective atomic number (Z(eff)) and electron density (N-el) are calculated by using mu/rho values. Besides, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) of inorganic metal halide cubic perovskites have been determined using the Geometric Progression (G-P) fitting method at energies 0.015-15 MeV up to penetration depths of 40 mean free path (mfp). The examined shielding parameters are highest in low energy region and lowest in the middle energy region. The results were discussed in relation to the contents of the samples. The lead-containing compounds are more efficient than the other compounds for shielding gamma radiations. Other perovskites (without lead) also have the ability to absorb radiation better than many other shielding materials currently used. Thus, the studied compounds may be effective in the production of novel shielding materials.
Gamma Shielding Properties of Tamoxifen Drug
(Amer inst Physics, 2017) Kanberoglu, Gulsah Saydan; Oto, Berna; Gulebaglan, Sinem Erden
Tamoxifen (MW=371 g/mol) is an endocrine therapeutic drug widely prescribed as chemopreventive in women to prevent and to treat all stages of breast cancer. It is also being studied for other types of cancer. In this study, we have calculated some gamma shielding parameters such as mass attenuation coefficient (mu(rho)), effective atomic number (Z(eff)) and electron density (N-el) for Tamoxifen drug. The values of lip were calculated using WinXCom computer program and then the values of Z(eff) and N-el were derived using lip values in the wide energy range (1 keV - 100 GeV).
Investigation of Structural, Electronic, and Dynamic Properties of Half-Heusler Alloys Xcub (X = Ti, Zr) by First Principles Calculations
(Wiley-v C H verlag Gmbh, 2021) Gulebaglan, Sinem Erden; Dogan, Emel Kilit
In order to find out the structural, electronic, and dynamic properties of TiCuB and ZrCuB half-Heusler alloys, density functional theory within the generalized gradient approximation is used by Quantum Espresso package program. The lattice parameters, bulk modulus, first derivation of bulk modulus, electronic band structure, phonon dispersion curves, and phonon density of states are calculated for both half-Heusler alloys. Electronic band structure plots exhibit that these alloys are in semiconductor structure. Dynamic properties are investigated using a density functional perturbation theory. Phonon dispersion curves show that TiCuB and ZrCuB are dynamically stable alloys. Only the calculated lattice parameters can be compared with the literature, and it is noticed that they are in a good agreement. The rest of the obtained results cannot be compared with the literature since these calculations are performed for the first time in the literature with this study.
Lattice Dynamics and Electronic Properties of Heusler Alloys Li2alx (X=ga, In): a Comparison Study
(Chinese Physical Soc, 2021) Dogan, Emel Kilit; Gulebaglan, Sinem Erden
The lattice parameters, bulk modulus, first derivative of the bulk modulus, electronic band structures, phonon dispersion curves and phonon density of states calculations for Li2AlGa and Li2AlIn Heusler alloys are performed and compared in this study using density functional theory within the generalized gradient approximation. Computed lattice parameters display a good agreement with the literature. Obtained electronic band structures of both Heusler alloys show that they are in semi-metallic structure. Phonon dispersion curves and the phonon density of states graphs are also obtained in order to study the lattice dynamics of these Heusler alloys. It is noticed that Li2AlGa and Li2AlIn Heusler alloys are dynamically stable in the ground state.
Lun'nin Yüksek Basınç Altında Yapısal, Elektronik ve Titreşimsel Özelliklerinin Dft ile İncelenmesi
(2021) Boz, Nazlı; Akyüz, Gonul Bilgeç; Tunali, Aylin Yildiz; Gulebaglan, Sinem Erden
Bu çalışmada, kaya tuzu yapısındaki kübik Lütesyum Nitrit (LuN) bileşiğinin yapısal, elektronik ve örgü dinamiği özellikleri, Genelleştirilmiş Gradyan Yaklaşımı ile Yoğunluk Fonksiyoneli Teorisine dayalı olarak incelenmiştir. Örgü sabitleri, yığın modülü ve yığın modülü türevi gibi yapısal özellikler literatürle iyi bir uyum içindedir. Yüksek simetri doğrultuları boyunca, farklı basınçlar altındaki fonon dağılım eğrileri Yoğunluk Fonksiyoneli Teorisi’nin Doğrusal Tepki Yaklaşımı’na uygun olarak elde edilmiştir. Elde edilen pozitif fonon dağılım eğrileri, incelenen tüm materyallerin kararlı olduğunu göstermektedir. Ayrıca, optik fonon bant aralığının artan basınçla arttığı bulundu. Buna göre, LuN’nin optoelektronik uygulamalar için gelecek vaat eden bir malzeme olması öngörülmektedir. Bu araştırmanın gelecekteki birçok çalışmaya ışık tutması bekleniyor.
Prediction the Structural, Electronic, Elastic and Dynamical Properties of Lialge and Liinge Half-Heusler Crystals by Density Functional Theory
(Elsevier, 2022) Gulebaglan, Sinem Erden; Dogan, Emel Kilit
In the present study, structural, electronic, elastic and vibrational properties of LiInGe and LiAlGe half-Heusler compounds are investigated using density functional theory implemented in ABINIT and Quantum ESPRESSO programs. Generalized gradient approximation as an exchange correlation functional is used in Kohn-Sham equations to find lattice parameters, energy band gaps and three elastic constants C-11, C-12 and C-44 for LiInGe and LiAlGe crystals. Density functional perturbation theory has been adopted in the study of lattice dynamics. As a result of the calculations, it is concluded that the phonon dispersion curves have positive frequency values throughout the entire Brillouin region and the dynamic stability of both crystals is strong. It is estimated as a result of calculations that this stabilization is impaired at a pressure value of approximately 492.65 kbar for LiInGe crystal and approximately 962.16 kbar for LiAlGe crystal.
Some Properties of Liinsi Half-Heusler Alloy Via Density Functional Theory
(indian Acad Sciences, 2021) Dogan, Emel Kilit; Gulebaglan, Sinem Erden
In this study, structural, electronic, elastic and dynamic properties for LiInSi in the half-Heusler structure were analysed with the generalized gradient approximation using the density functional theory. The results obtained are compatible with the structural and electronic properties in literature. In addition to the results related to electronic properties in literature, cohesive energy and formation energy values were calculated. These values were found to be 10.333 and -0.884 eV, respectively. Elastic constants, bulk, shear, Young's moduli, Poisson's coefficient and Zener anisotropy factor values of LiInSi alloy were revealed. In addition, using linear phonon theory, phonon dispersion curve and phonon density of states graph were obtained. It has been calculated that while the LiInSi alloy is dynamically stable in the ground state, it becomes unstable under nearly 615 kbar pressure. Elastic and dynamic properties are presented in literature for the first time. It is expected that these results will be a guide for future studies.
Structural Electronic and Dynamic Properties of Li3bi and Li2nabi
(Iop Publishing Ltd, 2020) Gulebaglan, Sinem Erden; Dogan, Emel Kilit
We report a study of structural, electronic and dynamic properties of Li3Bi and Li2NaBi via density functional theory. It is found that Li3Bi and Li2NaBi show semiconducting property with an indirect electronic band gap. The calculated structural and electronic parameters (lattice parameters, bulk modulus, bulk modulus derivation) are in a good agreement with the available experimental data. Full phonon spectra of Li3Bi and Li2NaBi materials in the Rock Salt structure were collected using the linear response method. At 0 GPa pressure, Li3Bi is dynamically stable while Li2NaBi, which can be synthesized from Li3Bi by replacing one Bi atom with the Na atom, is unstable. In this study we searched to find the pressure value that makes Li2NaBi dynamically stable. Calculations showed that the Li2NaBi structure becomes stable when 8.62 GPa pressure is applied to the Li2NaBi structure. This study is thought to give direction to the future studies.
Structural Electronic and Vibrational Properties Analysis of Li2cax (X = Sn, Pb) Heusler Alloys: a Comparative Study
(Iop Publishing Ltd, 2020) Gulebaglan, Sinem Erden
This study was focused on structural, electronic and vibrational properties of Li2CaSn and Li2CaPb with density functional theory. All properties of these compounds were computed by implementing General Gradient Approximation and using Quantum Espresso software programme. As a result of the calculations, it was found that the lattice parameter is 6.967 angstrom and bulk modulus is 33.94 GPa for Li2CaSn. Also, these values are 7.062 angstrom and 29.574 GPa for Li2CaPb. The calculated lattice parameters are in good agreement with the available experimental data. There is no previous theoretical calculation for Li2CaSn and Li2CaPb compounds. It was calculated that Li2CaSn and Li2CaPb have a semi-metal property. The full phonon dispersion curves of Li2CaSn and Li2CaPb compounds in the Heusler type structure were examined using the linear response method. Under 0 kbar pressure, Li2CaPb was unstable while Li2CaSn was dynamically stable. Calculations showed that when 38.42 kbar pressure is applied to the Li2CaPb compound, the Li2CaPb compound becomes dynamically stable. It is believed that this study will shape future studies.
Theoretical Insight on the Structural, Electronic, Elastic, Optical and Vibrational Properties of Ligasi Half-Heusler Crystal for Ground State and Under Pressure
(Springer, 2025) Gulebaglan, Sinem Erden; Dogan, Emel Kilit
In this study, the electronic, structural, optical, elastic and dynamic properties of LiGaSi half- Heusler crystalline were tried to be predicted for the ground state and under pressure by using density functional theory. Quantum Espresso and Abinit software programs were used while carrying out this research. While performing calculations in these package programmings, the Generalized Gradient Approximation was taken into consideration. Calculations showed that the critical pressure value for LiGaSi half-Heusler crystal is estimated to be approximately 935 kbar. It was noticed that the LiGaSi half-Heusler crystal, while a brittle material in the ground state, became an elastic material under pressure. Additionally, it was concluded that while LiGaSi half-Heusler crystal is dynamically stable in the ground state, LiGaSi half-Heusler is dynamically unstable under 935 kbar pressure. This has additionally been shown to make it more thermally conductive. It is thought that the results obtained from this study and the information obtained by interpreting the results will contribute to the literature and will be useful for future studies.
Yoğunluk Fonksiyonel Teorisi Aracılığıyla Yarı-heusler Bileşiği Liagse'nin Yapısal Elektronik Optik Elastik ve Fonon Özelliklerinin Tahmin Edilmesine İlişkin Öngörüler
(2022) Gulebaglan, Sinem Erden
LiAgSe yarı-Heusler yapısının yapısal, elektronik, optik, elastik ve dinamik özellikleri ilk prensip hesaplamaları ile incelenmiştir. LiAgSe yarı-Heusler bileşiği, Yoğunluk Fonksiyonel Teorisi kullanılarak Genelleştirilmiş Gradient Yaklaşımı ile incelendi. Yapısal, elektronik ve dinamik özelliklerini araştırmak için Quantum Espresso simülasyon programı, elastik ve optik özelliklerini araştırmak için ise ABINIT simülasyon programı tercih edilmiştir. Hesaplama sonucunda oluşan LiAgSe kristalinin elektronik bant yapısı grafiği, bu kristalin yarı metalik bir yapıya sahip olduğunu göstermektedir. LiAgSe hacmi için kompleks dielektrik sabiti, extinction katsayısı, reflectivity, gibi optik özellikler hesaplandı ve çizildi. Bu çalışmada, yoğunluk fonksiyonel teorisi kullanılarak, LiAgSe yarı-Heusler kristalinin elastik sabitleri bulk, Poisson oranı ve Debye Sıcaklık değerleri belirlendi. Bu özelliklerin dışında fonon dağılım eğrisi LiAgSe yarı-Heusler kristalinin temel durumda dinamik olarak kararlı olmadığı, yaklaşık 16.396 GPa basınç altında kararlı bir şekilde dönüştüğü hesaplanmıştır.
Yoğunluk Fonksiyoneli Teorisi ile Lialsi’un Basınç Altında Elektronik ve Titreşim Özellikleri
(2019) Gulebaglan, Sinem Erden
Li içerikli malzemeler teknolojinin gelişmesinde önemli yere sahiptirler. Bu nedenle Li içerikli kristallerin yapısal elektronik vedinamik özelliklerinin bilinmesi önemlidir. LiAlSi kristalinin yapısal, elektronik ve örgü dinamik özellikleri, ab-initio psödopotensiyelmetodu ve Genel Gradyent Yaklaşımı ile doğrusal bir tepki ile gerçekleştirilmiştir. LiAlSi kristali Zincblende yapıda olup uzay grubu$F\\overline43m$'dir. LiAlSi kristalinin örgü parametresi 6.0306 Å olarak bulunmuştur. Hesaplanan örgü parametresi, yığın modulü ve yığınmodülünün birinci dereceden basınca göre türevi, deneysel ve diğer teorik hesaplamalar ile uyumludur. Elektronik band yapısı vefonon dağılım eğrisi, Quantum Espresso programı kullanılarak analiz edilmiştir. Fonon dağılım eğrisi ve fonon durumların yoğunluğu,yoğunluk fonksiyonel pertürbasyon teorisi ile hesaplanmıştır. Fonon frekans değerleri pozitif olduğundan LiAlSi kristali kararlıyapıdadır. Daha sonra P= 8.892 GPa basınç altında elektronik band yapısı ve fonon dağılım eğrisi incelenmiştir. P=0.0 GPa basınçtaLiAlSi kristali yarıiletken özelliği gösterirken P= 8.892 GPa basınç uygulandığında iletken özelliği gösterdiği ortaya konmuştur. Bubasınç değerinde de fonon frekans değerleri pozitiftir. Ayrıca iki farklı basınç altında (P=0.0 GPa ve P=8.892 GPa) Γ, X ve L yükseksimetri noktalarındaki enine, boyuna akustik ve enine, boyuna optik mod değerleri listelenmiştir. Bu çalışmanın sonuçlarının literatürekatkı sağlayacağı düşünülmektedir.