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Öğe Effect of Co and Mn Doping on the Electronic and Magnetic Properties of XC₂ (X = Hf, Zr) MXene Monolayers: A First-Principles Study(John Wiley and Sons Inc, 2025) Bölen, Emre; Alyörük, Meryem DeryaMXenes, particularly Hf₂C and Zr₂C monolayers, exhibit exceptional electronic and magnetic properties, making them promising candidates for advanced applications. In this study, the effects of Co and Mn doping on Hf₂C and Zr₂C are investigated using first-principles calculations. The revPBE exchange-correlation functional is identified as yielding the lowest energy configurations. Molecular dynamics simulations confirm the structural stability of the doped systems, with no signs of phase transitions or instabilities. Doping significantly alters the electronic band structures and magnetic properties. Co doped Hf₂C displays a bandgap, making it suitable for infrared detectors and low-temperature sensor applications, while Mn doping lead to a significant enhancement of the net magnetic moments relative to the pure monolayers. Applying an external electric field results in significant changes in the magnetic moment, particularly in Co doped Hf₂C and Zr₂C monolayers, highlighting their strong sensitivity to electric-field-induced perturbations and suggesting potential utility in orbitronic applications. These findings highlight the versatility of doped MXene monolayers, paving the way for their use in spintronic devices, detectors, and sensors.Öğe Investigation of the Electronic Structure in GaAs/AlxGa1-xAs Quantum Dots with Four Electrons(John Wiley and Sons Inc, 2025) Çakır, Bekir; Yakar, Yusuf; Özmen, AyhanIn this paper, a detailed analysis of the electronic structure of four-electron quantum dots is performed with finite confinement potential by a modified variational optimization approach based mainly on the quantum genetic algorithm and the Hartree-Fock-Roothaan method. For the ground and higher excited configurations, our analysis covers a range of parameters like the average energies of ground and excited states, singlet and triplet state energies, orbital energies, and two-electron Coulomb and exchange interaction energies. One-electron kinetic energy, the Coulomb potential energy between electrons and impurity, the confinement potential energy for the electrons, and the probability of finding an electron inside or outside the quantum well are also studied. The results demonstrate that both spatial confinement and the height of the potential barrier have a pronounced effect on all energies in the strong and intermediate confinement regions, but this influence weakens significantly in large dot radii. The most substantial difference between singlet and triplet energies occurs in the 1s22s2p configurations, with this difference decreasing in higher configurations. Significant increases in the 1s and 2s orbital energies are observed at the dot radii where the 2p, 3d, and 4f electrons from the outermost orbit begin to penetrate the well.Öğe Sodium-induced phase shift in α-NaMnO2 and electrochemical properties of the full cells using hard carbon anodes derived from regional olive leaves(Springer, 2025) Doğan, Ebru; Özcan, Sibel; Aksu Canbay, Canan; Karta, Mesut; Depci, Tolga; Altın, SerdarIn this study, we investigated the effect of excess sodium (Na) in a NaMnO2 structure using one-step heat treatment at 900 °C followed by quenching in liquid nitrogen (N₂). According to the X-ray diffraction (XRD) analysis, there was a competition between the monoclinic and orthorhombic phases, and we found that there were two monoclinic phases with similar structural properties. Therefore, we focused on revealing the formation of two isostructures of the monoclinic phase triggered by Na ions. We found that the lattice parameters and β angle changed from 113° to 105° in the samples with increasing Na content. Structural analysis of the powders using the XRD data was conducted using Rietveld refinement, and the phase ratios for all samples were calculated. The sample with x = 1.3 showed a 95% α-phase. To understand the formation of the two isostructures, we performed Density functional theory (DFT) calculations to examine their band structure, stability, and formation energy. A structural analysis of the excess Na-doped samples was performed using common techniques, and it was found that excess Na caused the formation of a coating on the grains in the form of sodium oxide. To validate this prediction, we conducted inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy coupled with energy dispersive X-ray (SEM–EDX) analyses using the basic properties of these techniques and their interactions with materials. In the second part of the study, we produced HC from locally sourced olive leaves and investigated their structural properties. The electrochemical properties of the electrode materials were examined using a half-cell configuration as electrodes with Na metal and a full-cell configuration using x = 1.3 cathode and HC anode. A direct-contact pre-sodiation strategy was used as the anode in the full-cell measurements. It was found that the full cells had initial capacity values of 150 mAh/g for the voltage range 1.5–4.3 V and 120 mAh/g for the voltage range 1.5–3.5 V.Öğe Physical properties of Mo2C monolayer by substitutional doping with Co/Cu atoms(Springer Nature, 2025) Bölen, Emre; Deligöz, Engin; Özışık, H.Monolayer Mo2C, a member of the MXene family, uniquely combines metallic and semiconducting properties, making it a promising candidate for various applications such as electronics, energy storage, thermoelectric, and spintronic. This study reported a comprehensive investigation of the structural, mechanical, dynamical, electronic, magnetic, and transport properties of pure and doped Mo2C monolayers using first-principles density functional theory. The transport properties are investigated in terms of transmission spectrum and pathways. The Mo2C shows dynamical and mechanical stability, auxetic behavior with negative Poisson's ratio, high isotropic mechanical stability and good electrical conductivity. Transition metal atoms, cobalt (Co) and copper (Cu) doping, were used to optimize the properties of the material. Electronic band structure analysis confirms the metallic nature of both pure and doped Mo2C. The result of the present study provides insight into how to improve the electronic transport properties of pure and doped Mo2C, which is used in spintronic applications.Öğe Cl−, Na+ and Mg2+ Adsorption and Electronic Properties on 2-Octyl Acrylate and Isobornyl Acrylate Monomers: A Comprehensive DFT Study(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Bölen, Emre; Dolado, Jorge S.; Ayuela, AndrésThe design of advanced functional materials from polymers involving 2-octyl acrylate and isobornyl acrylate monomers is crucial for applications such as biofouling resistance, coatings, UV-curable films, and use in marine environments. In this study, we investigated the adsorption and electronic properties of 2-octyl acrylate and isobornyl acrylate monomers in the presence of Cl−, Na+, and Mg2+ ions using Density Functional Theory calculations. Adsorption energies, quantum descriptors, and electrostatic potential maps were analyzed to elucidate ion-specific interactions with these monomers. Our findings indicate that Mg2+ ions exhibit the strongest interactions due to their high charge density, followed by Na+ and Cl− ions, which show moderate and weak adsorption, respectively. Density of states analyses revealed that Mg2+ significantly lowers HOMO and LUMO levels, narrowing the gap and stabilizing the system, while Cl− ions result in a smaller gap and weaker interactions. Electrostatic potential maps further confirmed these trends, correlating ion adsorption sites with molecular charge distributions. This study highlights the critical role of ion adsorption and its associated electronic properties and paves the way for future advancements in optimizing 2-octyl acrylate and isobornyl acrylate-based materials for applications such as coatings and use in marine environments.Öğe Lead-Free Na2ZrTeO6 Double Perovskite: A Promising Candidate for High-Temperature and Optoelectronic Applications(John Wiley and Sons Inc, 2025) Deligöz, Engin; Rached, D.; Özışık, H.; Caid, M.; Rached, Y.The double perovskite class of materials is highly significant due to its optoelectronic properties and structural stability, making it ideal for applications in electronics, photovoltaics, and catalysis. We present a first principles study of the elastic, anisotropic mechanical, electronic, and optical properties of the newly synthesized double perovskite Na2ZrTeO6 compound. The calculated elastic constants confirm the mechanical stability of the compound. Na2ZrTeO6 exhibits high mechanical durability, a wide band gap, and significant anisotropic mechanical properties. The observed anisotropy suggests that Na2ZrTeO6 may exhibit direction-dependent mechanical and electronic behavior, making it a versatile material for advanced technological applications. The high Debye and melting temperature indicate that Na2ZrTeO6 may be very suitable for high-temperature processes, refractory materials, and high-temperature equipment. This compound is a semiconductor with a wide band gap and the electrons are mobile carriers because they have smaller effective masses. The optical properties, including the real and imaginary parts of the complex dielectric function, energy loss, real and imaginary parts of the refractive index, and absorption coefficient, are analyzed for photon energies up to 20 eV to evaluate the optical response.Öğe Electrical properties, conduction mechanisms, and voltage dependent curves of interface traps, series resistance in Au/(Sn:Fe2O3)/n-Si structures using impedance measurements(Springer, 2025) Baştuğ, A.; Khalkhali, A.; Sarıtaş, S.; Yıldırım, M.; Güçlü, Ç.Ş.; Altındal, Ş.In this work, electrical properties in the constructed Au/(Sn:Fe2O3)/n-Si (MIS/MOS) structures have been analyzed using impedance-spectroscopy model (ISM) in wide range frequency and voltage to get more accuracy and reliable results on the electrical parameters, interface traps (Nss or Dit) and conduction mechanisms. The doping donor-atoms (Nd), diffusion-potential (Vd), barrier-height (Φb), depletion layer width (WD) was calculated from the slope/intercept of the C−2-V plots for various frequencies. The Nss and their life/relaxation times (τ) versus voltage profiles was extracted from conductance technique. The observed some changes in these-parameters were explained by the interlayer, Rs, Nss polarization. However, while the Nss and Maxwell–Wegner polarization are usually dominate in inversion and depletion zones at lower-frequencies, Rs and interlayer dominate only at accumulation zone at higher-frequencies. The Rs vs V curves for various frequency were also extracted from the Nicollian & Brews technique. The obtained results are indicated that the interlayer, Nss, and polarization are more dominate on the ISM which is considering in calculation of electrical features.Öğe Physical characteristics of Pb2FeSbO6 double perovskite for thermoelectric applications(Elsevier B.V., 2025) Caid, Messaoud; Rached, Djamel; Deligöz, Engin; Rached, Youcef; Rached, Habib; Irfani, MuhammadThe structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of Pb2FeSbO6 double perovskite are investigated using full-potential linear augmented plane-wave (FP-LAPW) method incorporating the generalized gradient approximation (GGA) and GGA plus onsite Coulomb parameter (GGA + U). Pb2FeSbO6 crystallizes in a ferromagnetic (FM) cubic structure (space group Fm-3m) with lattice constants of 8.072 Å, in good agreement with experimental data. The compound exhibits ductile behavior, as assessed by Poisson and Pugh's ratios. It shows an integer magnetic moment of 5.00μB per formula unit and demonstrates semiconductor behavior with bandgaps as follows: under GGA, the band-gap is 2.347eV (Γ-X) in spin-up and is 1.208eV (X-Γ) in spin-down; under GGA + U, the band-gap is 2.923eV (X-Γ) in spin-up and is 1.665eV (X-X) in spin-down. Optical properties reveal strong absorption in the ultraviolet range, and thermoelectric evaluation suggests a promising figure of merit (ZTmax ≈ 1.0 at 300 K). These findings underscore the potential of Pb2FeSbO6 for thermoelectric and optoelectronic applicationsÖğe Small gas adsorption on metal clusters on trimer form of graphyne: First-principles density functional theory study(Elsevier B.V., 2025) Küçük, Hilal; Akça, AykanGraphyne has been a popular two-dimensional surface since its synthesis. Many studies have been contributed to the material science literature with graphyne due to its carbon-based nature, lightweight properties, and excellent properties. This research represents a first-principles study of the adsorption of small gas molecules (CO, NH3, SO2, NO, and NO2) on transition metal clusters (TM = Cu and Co) doped on graphyne. The cluster is designed with three metal atoms on a trimer form of graphyne. These two surfaces are formed with high stability with the binding energy of −3.91eV and −2.47eV. The geometric, magnetic, and electronic behaviors of the adsorptions are considered. ICHOP values are tested to demonstrate a deep understanding of bond strength. Although one configuration of CO molecule from the oxygen site physically interacts with the 3Co/GY surface, other molecules and CO from the carbon site attract with chemical interactions on both surfaces. All adsorptions have significant electron exchanges except the configuration of CO from the oxygen site and NH3 on Co-doped graphyne. Unlike other molecules, only NH3 molecules are electron donors. It is encouraging that 3Co/GY sensor might be able to detect NH3 at high temperatures.Öğe Understanding the pressure effect on the physical properties of half-Heusler semiconductor LiCaX (X = As, Sb, N) compounds from Ab-initio calculations(Elsevier, 2025) Çiftçi, Yasemin O.; Koçak, Belgin; Ateşer, EnginThe study delves into the structural, elastic, electronic, thermodynamic, and lattice dynamical and optic properties of LiCaX (X = As, Sb, N) ternary half-Heusler compounds under varying pressure and temperature conditions. Employing density functional theory with the generalized gradient approximation (GGA) in VASP codes, the initial steps involve optimizing the structure of the compound (cubic MgAgAs-type, space group F43m, C1b), determining elastic constants (C11, C12, and C44), and calculating elastic moduli (bulk modulus, shear modulus, Young's modulus). Other mechanical parameters such as Pugh's ratio, Poisson's ratio, and Zener anisotropy factor are also derived, providing insights into the brittle/ductile characteristics and isotropic/anisotropic behavior. The study further explores different vibrational modes in the compounds, and the effects of pressure on elastic anisotropy, vibrational, and optical properties are thoroughly investigated. Utilizing the quasi-harmonic Debye model, the research successfully reports V/Vo, bulk modulus, thermal expansion coefficient, and heat capacity at constant volume over a temperature range from 0 to 1000 K. The variation of photon energy is analyzed concerning the real and imaginary parts of the dielectric constant, refractive indices, extinction coefficient, reflectivity, and energy loss function up to 20 eV. The findings encapsulate the fundamental physical properties of all considered compounds, concluding with suggestions for potential future research avenues.Öğe Small gas adsorption on metal clusters on trimer form of graphyne: First-principles density functional theory study(Elsevier, 2025) Küçük, Hilal; Akça, AykanGraphyne has been a popular two-dimensional surface since its synthesis. Many studies have been contributed to the material science literature with graphyne due to its carbon-based nature, lightweight properties, and excellent properties. This research represents a first-principles study of the adsorption of small gas molecules (CO, NH3, SO2, NO, and NO2) on transition metal clusters (TM = Cu and Co) doped on graphyne. The cluster is designed with three metal atoms on a trimer form of graphyne. These two surfaces are formed with high stability with the binding energy of -3.91eV and -2.47eV. The geometric, magnetic, and electronic behaviors of the adsorptions are considered. ICHOP values are tested to demonstrate a deep understanding of bond strength. Although one configuration of CO molecule from the oxygen site physically interacts with the 3Co/GY surface, other molecules and CO from the carbon site attract with chemical interactions on both surfaces. All adsorptions have significant electron exchanges except the configuration of CO from the oxygen site and NH3 on Co-doped graphyne. Unlike other molecules, only NH3 molecules are electron donors. It is encouraging that 3Co/GY sensor might be able to detect NH3 at high temperatures.Öğe DFT assessment on the future prospects of inorganic lead-free halide double perovskites Cs2ABI6 (AB: GeZn, SnBe) for energy conversion technologies(Elsevier B.V., 2024) Caid, Messaoud; Rached, Habib; Rached, Djamel; Özışık, Hacı; Delig?z, Engin; Rached, YoucefIn this study, we employed density functional theory (DFT) calculations to investigate the structural, elastic, electronic, optical, and thermoelectric properties of Cs2ABI6 (AB: GeZn, SnBe) halide double perovskites (HDPs). We employed the full-potential linear augmented plane-wave (FP-LAPW) method, incorporating the generalized gradient approximation (GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) approach for the exchange-correlation potential. We found that the HDPs are stable in a cubic structure (space group Fm-3m), as indicated by phase stability analysis, formation energies, tolerance factor, and elastic constants. The compounds exhibits ductile behavior, as assessed by Poisson's and Pugh's ratios. The electronic band structures of Cs2GeZnI6 and Cs2SnBeI6 exhibit indirect band gaps (X-L) of 1.124 eV and 1.551 eV, respectively, as calculated using the TB-mBJ approximation. Optical spectra were evaluated over the 0–13 eV energy range, including the dielectric functions, extinction coefficient, electron energy loss, refractive index, optical conductivity, reflectivity, and absorption coefficient. Additionally, we calculated thermoelectric parameters across a range of chemical potentials and temperatures to assess their suitability for thermoelectric applications. Our results suggest that these compounds are highly promising candidates for both optoelectronic and thermoelectric devices.Öğe Ab Initio Computational Materials Science(ICMATSE, 2024) Deligöz, EnginAb initio ((Latin for “from the beginning”) computational materials science is play an important role in accelerating the development and optimization of new materials. It is widely used in materials science. The aim is to simulate the properties of materials in order to understand and complement experiments. Scientists use these methods in the discovery of new materials, materials design, catalysis and chemical reaction mechanisms. Ab initio method (often referred to as firstprinciples methods) contains no experimental input other than the fundamental physical constants, making it possible to analyze the properties of systems that are difficult to characterize experimentally, or to predict the physical properties of materials that have not yet been made. We present an overview of the capabilities of ab initio methods in the structural and mechanical properties, illustrated with an example for 2D orthorhombic ?-GeSe compound using the VASP computer program.Öğe Impact of van der Waals corrected functionals on monolayer GeSe polymorphs: An in-depth exploration(Elsevier B.V., 2025) Kutluca, Abdullah; Deligöz, Engin; Özışık, HacıA comprehensive ab initio calculations were conducted to analyze the structural, electronic, elastic, and phonon characteristics of monolayer GeSe polymorphs, utilizing various van der Waals corrections. The physical properties of layered GeSe polymorphs were investigated using the Perdew-Burke-Ernzerhof exchange–correlation functional, implemented within a generalized gradient approximation. The study presents findings on the effects of the DFT-D3 and DFT-D3(BJ) functionals with Grimme correction on the ground state properties, with a focus on weak van der Waals interactions. The mechanical and dynamic stability of monolayer GeSe polymorphs is indicated by the analysis of the elastic constants and phonon dispersion curves. Monolayer GeSe polymorphs are found to have an indirect band gap semiconductor structure using HSE06 for the considered phases. The band gaps of these polymorphs are predicted to range from approximately 0.95 to 2.47 eV, which falls within a highly useful energy range for practical applications. Additionally, this study is the first to investigate the anisotropic mechanical properties of these materials.Öğe A first principles study of cubic IrO2 polymorph(Springer Nature, 2007) Deligöz, Engin; Çolakoğlu, Kemal; Öztekin Çiftçi, YaseminWe have studied structural, thermodynamic, elastic, and electronic properties of cubic IrO 2 polymorph via ab initio calculations within the LDA and GGA approximations. Basic physical properties, such as lattice constant, bulk modulus, second-order elastic constants (C ij), and the electronic band structures are calculated, and compared with available experimental values. We have, also, predicted the Young's modulus, Poison's ratio (?), Anisotropy factor (A), sound velocities, and Debye temperature.Öğe Lattice dynamical calculations for the bcc cerium(Elsevier, 2005) Deligöz, Engin; Çiftçi, Yasemin; Çolakoğlu, KemalLattice dynamical calculations are performed on cerium with bcc structure using the improved third-neighbor Clark–Gazis–Wallis (CGW) model. The theory has been applied to compute the dispersion curves, frequency spectra, lattice specific heat, and Debye temperature of the bcc cerium. In general, the obtained results agree reasonably well with the experimental data at the high temperature of the bcc cerium which has been very recently measured by K. Nicolaus et al.Öğe Elastic, electronic, and lattice dynamical properties of CdS, CdSe, and CdTe(Elsevier, 2006) Deligöz, Engin; Çolakoğlu, Kemal; Çiftçi, Y.Ab initio calculations, based on norm-conserving pseudopotentials and density functional theory, have been performed to investigate elastic, electronic and lattice dynamical properties of chalcogenides (CdS, CdSe, and CdTe). The calculated lattice parameters, elastic constants, band structures, and phonon dispersions are in good agreement with available experimental and theoretical results. We also presented the pressure-dependence of elastic constants and the pressure-dependence of band gaps.Öğe First-principles studies on structural and electronic properties of ThN(AIP Publishing, 2007) Arslan, S.; Çiftçi, Y.Ö.; Çolakoğlu, Kemal; Deligöz, EnginWe present an ab?initio study of the structural and electronic properties of ThN. The plane?wave pseudopotential approach to the density?functional theory within the generalized?gradient approximation implemented in VASP(Viena Ab?initio Simulation Package) is used. The calculated lattice parameter, elastic constants and band structures are compared with the available experimental and the other theoretical results, and good agreement is obtained.Öğe The first?principles calculations on the CuI compounds(AIP Publishing, 2007) Yüce, G.; Çolakoğlu, Kemal; Deligöz, Engin; Çiftçi, Y.Ö.The ab initio total energy calculations, based on norm?conserving pseudopotentials and density functional theory, have been performed to investigate some structual, elastic, electronic and lattice dynamical properties of CuI in zinc blende (B3) and rock?salt (B1) structures. The calculated structural parameters, elastic moduli, band structures and the phonon dispersion curves are compared with the available experimental and the other theoretical works, and generally good results obtained. We have, also, presented the pressure dependent behaviours of the elastic constants for the same compound.Öğe Ab?Initio total energy calculations on the AlBi compound(AIP Publishing, 2007) Deligöz, Engin; Çolakoğlu, Kemal; Çiftçi, Y.Ö.We present the results of the structural, thermodynamical, elastic, and electronic properties of the hypothetical aluminum bismuth (AlBi) compound (III?V) in zinc?blende phase by performing ab initio total energy calculations within the local density approximation in Siesta package. Particularly, we have focused on the pressure dependences of the second?order elastic constants (Cij), Debye temperature, and Melting temperature for this compound. Calculations on the other basic properties, such as lattice constant, bulk modulus, and some band structural parameters are also repeated and compared with those of other recent theoretical works, and generally, the good agreements are obtained.
