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Item The Structural, Elastic, Electronic and Thermodynamical Properties of CaBi: A First-Principles Study(Boğaziçi University, 2008) Deligöz, Engin; Çolakoğlu, Kemal; Çiftçi, YaseminWe have studied some structural, thermo dynamical, elastic, and electronic properties of CaBi in non- magnetic states without spin polarization by performing ab initio calculations within the LDA approximations. The some basic ground state physical properties, such as lattice constant, bulk modulus, second-order elastic constants (Cij), the phase transition pressure from the NaCl (RS) to CsCl (B2) structure, and the electronic band structures for the most stable phase, are calculated, and compared with the other theoretical work. In order to gain some further information, we have, also, predicted the Young’s modulus, Poison ratio (?), Anisotropy factor (A), sound velocities, and Debye temperature for B1 phase, and the reasonable values are found.Item Effect of Chronic Immobility Stress and High Salt Diet on Brain Tissue Memory Markers in Rats(Wiley, 2023) Türkgüven, Yaren; Şimşek, Hasan...Item BaGe3 Bileşiğinin Mekanik ve Titreşimsel Özellikleri: Ab-initio Çalışması(Adnan MenderesÜniversitesi, 2018) Özdemir, Seda; Özışık, Havva; Özışık, Hacı; Altay, Mehtap; Deligöz, EnginBu çalışmada tetragonal yapıda (I4/mmm, No. 139) kristalize olduğu bilinen BaGe3 bileşiğinin yapısal, mekanik ve titreşimsel özellikleri VASP paket programı ile DFT kullanılarak hesaplandı. Hesaplamalarda elektron iyon etkileşimi için PAW metodu ve elektron-elektron etkileşimi için ise PBE değiş-tokuş ve korelasyon fonksiyoneli temel alındı [2-4]. Enerji minimizasyonu sonucu elde edilen örgü parametrelerinin deneyle uyumlu olduğu görüldü. Elastik sabitler “zor-zorlama” yöntemi kullanılarak hesaplandı ve bileşiğin mekaniksel olarak kararlı olduğu bulundu. Buradan elde edilen veriler yardımı ile polikristal mekanik özellikler hesaplandı. Ayrıca, yoğunluk fonksiyonel pertürbasyon teorisi kullanılarak fonon dağınımı ve fonon durum yoğunlukları çizdirilerek yorumlandı.Item Dy3Sİ5N9O Bileşiğinin elastik anizotropisi ve elektronik özellikleri(Adnan Menderes Üniversitesi, 2018) Altay, Mehtap; Özışık, Hacı; Deligöz, Engin; Ateşer, Engin; Özışık, HavvaHenüz yeni yapılan bir çalışmada nadir toprak elementlerinin oksonitridosilikat RE3[Si5N9O] (RE=Dy- Er, Yb) bileşikleri sentezlenmiş ve ortorombik Pbcm (no: 57, Z=4) yapıda kristal oluşturdukları belirlenmiştir [1]. Bu çalışmada, Dy3Si5N9O için kuramsal hesaplamalar yapılmıştır. Hesaplamalarda DFT-GGA dahilinde elektron iyon etkileşimi için PAW düzlem dalga metodu ve elektron-elektron etkileşimi için ise Perdew-Burke-Ernzerhof (PBE) değiş-tokuş ve korelasyon terimi temel alınarak VASP paket programında yapıldı. [2-4]. Elektronik band yapısı, durum yoğunluğu (DOS), parçalı durum yoğunluğu (PDOS) ve yük yoğunluğu hesaplanarak yorumlandı. 2. dereceden elastik sabitler (Cij) “zor-zorlama” yöntemi [5] kullanılarak elde edildi ve bunlara bağlı bileşiğin polikristal elastik modülleri yönelime bağlı incelendi. Ayrıca evrensel anizotropi faktörü hesaplanarak yorumlandı.Item CaGe3 Bileşiğinin Mekanik ve Elektronik Özelliklerinin Yoğunluk Fonksiyonel Teorisi ile İncelenmesi(İzmir Yüksek Teknoloji Enstitüsü, 2018) Özdemir, Seda; Özışık, Havva; Özışık, Hacı; Altay, Mehtap; Deligöz, EnginBu çalışmada tetragonal yapıda (I4/mmm, No. 139) kristalize olduğu bilinen CaGe3 bileşiğinin yapısal, mekanik ve elektronik özellikleri VASP paket programında Yoğunluk Fonksiyonel Teorisi (DFT) kullanılarak hesaplandı. Hesaplamalarda elektron iyon etkileşimi için PAW düzlem dalga metodu ve elektron-elektron etkileşimi için ise Perdew-Burke- Ernzerhof (PBE) değiş-tokuş ve korelasyon terimi temel alındı. Geometrik optimizasyon sonucu elde edilen örgü parametrelerinin deneysel verilerle uyumlu olduğu bulundu. Elektronik band yapısı ve durum yoğunluğu (DOS) hesaplanarak yorumlandı. Elastik sabitler “zor-zorlama” yöntemi kullanılarak hesaplandı ve bileşiğin mekaniksel olarak kararlı olduğu bulundu. Buradan elde edilen veriler yardımı ile polikristal mekanik özellikler hesaplandı.Item Tb3Si5N9O Bileşiğinin Mekanik ve Elektronik Özelliklerinin Yoğunluk Fonksiyonel Teorisi ile İncelenmesi(İzmir Yüksek Teknoloji Enstitüsü, 2018) Altay, Mehtap; Özışık, Hacı; Deligöz, EnginNadir toprak elementlerinin oksonitridosilikatları RE 3[Si 5N9 O] ortorombik Pbcm (no: 57, Z=4) yapıda kristal oluşturdukları yeni yapılan bir çalışmadan bilinmektedir [1]. Bu çalışmada, aynı serinin deneysel sentezi yapılmamış Terbiyum oksonitridosilikat Tb3 [Si5 N 9O]’ın üzerine belirlenen yapı örnek alınarak kuramsal hesaplamalar yapılmıştır. Hesaplamalarda Yoğunluk Fonksiyonel Teorisi-Genelleştirilmiş Gradyant Yaklaşımı (DFT-GGA) dahilinde elektron iyon etkileşimi için PAW (Projector-Augmented- Wave) düzlem dalga metodu ve elektron-elektron etkileşimi için ise Perdew-Burke-Ernzerhof (PBE) değiş- tokuş ve korelasyon terimi temel alındı ve VASP paket programı kullanıldı [2-4]. Elektronik band yapısı ve durum yoğunluğu (DOS) hesaplanarak yorumlandı. 2. dereceden elastik sabitler (Cij) “zor-zorlama” yöntemi [5] kullanılarak elde edildi ve bileşiğin polikristal elastik modülleri (Bulk ve Young modülü, Poisson oranı) ve evrensel anizotropi faktörü hesaplanarak yorumlandı.Item The Mechanical Properties of ZrSbTe and HfSbTe Compounds(OP125, 2016) Deligöz, Engin; Özışık, Hacı; Boğaz Özışık, HavvaBy means of first principles calculations, we have studied the structural and mechanical properties of the ZrSbTe and HfSbTe compounds. The elastic constants of these compounds are calculated, then bulk modulus, shear modulus, Young’s modulus, Possion’s ratio and Debye temperature of polycrystalline aggregates have been derived and relevant mechanical properties are discussed. We have found that these compounds have mechanically stable.Item The Magnetic and Electronic Properties of Ce1-xPrxIn3 Compounds(OP123, 2019) Boğaz Özışık, Havva; Özışık, Hacı; Deligöz, EnginThe ab initio total energy calculations have been performed to investigate the structural, magnetic, and electronic properties of the Pr doped CeIn3 compound in AuCu3 structure. Spin-polarized electronic band structure and density of states (DOS) were calculated and interpreted. The magnetic moments of the Pr doped CeIn3 compound was calculated. The obtained data were compared with the available experimental and theoretical work.Item Vibrational stability of RNiAl3 (R=Sc, Y) Compounds(Book of Proceedings, 2019) Altay, Mehtap; Özışık, Hacı; Deligöz, Engin; Boğaz Özışık, HavvaWe have used to ab-initio methods for determining the vibrational and thermodynamical properties for the ScNiAl3 and YNiAl3 compounds in orthorhombic Pnma structure (Space Group No: 62). The pseudopotential plane-wave approach is used based on density functional theory and implemented in the VASP package. The present phonon frequencies of ScNiAl3 and YNiAl3 compounds are calculated using the Phonopy code and DFPT methods. Also, the temperature dependent free energy, entropy and heat capacity quantities were calculated and discussed.Item Mechanical and Anisotropy Properties of Trigadolinium Heptanickel Tetradecaaluminide (Gd3Ni7Al14) Compound(Book of Proceedings, 2019) Özışık, Hacı; Deligöz, Engin; Boğaz Özışık, HavvaGd3Ni7Al14 compound is in the hexagonal P-62m structure. We have studied the structural, electronic, elastic and anisotropy properties. We have been used strass-strain method to predict the second order elastic constants (Cij) of the titled compound within the density functional theory. Our results showed that the compound is satisfy mechanical stability for the considered structure. The polycrystalline aggregate behavior estimated using the elastic constants. The bulk modulus, shear modulus, Young’s modulus, Possion’s ratio, Debye temperature, and anisotropy value of polycrystalline aggregates have been derived and relevant mechanical properties are discussed.Item The mechanical and anisotropy properties of ?-RuCl3 compound((WITAM-2018), 2018) Deligöz, Engin; Boğaz Özışık, Havva; Özışık, HacıThe recent study showed that the low-temperature crystal structure is described by space group C2/m with lattice parameters a=5.981 Å, b=10.354 Å, c=6.014 Å, and ?=108.800. Also, the recent theoretical paper described spin ordered states where FM is ground. In this study, we have studied the structural, mechanical, and directional dependency of mechanical properties of the ?-RuCl3 in monoclinic C2/m structure. The elastic constants of these compounds are calculated, then bulk modulus, shear modulus, Young’s modulus, Possion’s ratio, Debye temperature, and anisotropy value of polycrystalline aggregates have been derived and relevant mechanical properties are discussed. Furthermore, the directional dependence of the polycrystalline elastic modulus and Poisson's ratio are analyzed from calculated single-crystal elastic constants.Item The First-Principle Study on The Holmium Oxonitridosilicate (Ho3Si5N9O) Compound: Mechanical and Electronic Properties((WITAM-2018, 2018) Altay, Mehtap; Özışık, Hacı; Özışık, Havva; Deligöz, EnginWe have used to ab-initio methods for determining the structural, electronic, and elastic properties for the Ho3Si5N9O compound in the orthorhombic Pbcm structure (Space Group No:57, Z=4). The DFT-PBE and PPPAW approaches are used for predictions which implemented in the VASP package. We have computed the basic physical parameters such as lattice constants, bulk modulus, elastic constants. The calculations reveal that Ho3Si5N9O is mechanically stable and that an indirect band gap semiconductor compound.Item Structural determination and physical properties of CuB2 a first principles study((WITAM-2018), 2018) Deligöz, Engin; Boğaz Özışık, Havva; Özışık, HacıThe structural determination, thermodynamic and mechanical properties of CuB2 compound are systematically investigated by first-principles within the density functional theory (DFT). The titled compound is considered in AlB2, ReB2, and OsB2-type structures. The two different flavor PAW potentials (LDA-CA and GGA-PBE) are used to determine the properties. The mechanical stability is confirmed via the calculated elastic constants for in the ReB2 phases. In order to gain some further information, we have predicted the bulk modulus, shear modulus, Young’s modulus, Poison ratio (?), Anisotropy factor (A), sound velocities, and Debye temperature for the titled compound in the stable structure and the reasonable values are found. The obtained results are compared with the available data.Item First Principles Study of structural electronic and thermoelectric properties of Mo2ScAlC2((WITAM-2018), 2018) Bölen, Emre; Deligöz, Engin; Özışık, Hacı; Özışık, HavvaIn this study, the structural, electronic and thermoelectric properties of belong to MAX phase, Mo2ScAlC2 are investigated by within the framework of the density-functional theory (DFT) using the plane-wave pseudopotential approach and Boltzmann transport theory as implemented within the MedeA-VASP package. We have computed the structural parameters and electronic band structure of Mo2ScAlC2. All results are in agreement with the available experimental data and other theoretical calculations. We also calculated Seebeck coefficient, electrical conductivity, and electronic thermal conductivity and discussed in detail.Item A first principles study on the orthorhombic ScNiAl3((WITAM-2018), 2018) Altay, Mehtap; Özışık, Hacı; Özışık, Havva; Deligöz, EnginWe have used to ab-initio methods for determining the structural, electronic, and elastic properties for the ScNiAl3 compound in orthorhombic Pnma structure (Spg No:62). The pseudopotential plane-wave approach is used based on density functional theory and implemented in the VASP package. We have computed the basic physical parameters such as lattice constants, bulk modulus, elastic constants. The elastic constants are calculated using stress-strain relationship and their corresponding elastic moduli of polycrystalline aggregate, including shear moduli (G), Young’s moduli (E), Poisson’s ratios (?), and elastic anisotropy values (A) are obtained. The electronic band structures, total and partial density of states of these materials are given. The calculations reveal that ScNiAl3 is mechanically stable and have a soft-ductile nature metallic compound.Item The first principles structural study on the Barium Oxonitrido silicate BaSi4O6N2 compound((WITAM-2018), 2018) Özışık, Hacı; Deligöz, Engin; Boğaz Özışık, HavvaBy means of first principles calculations, we have studied the structural, electronic, elastic and anisotropy properties of the Barium Oxonitrido silicate (BaSi4O6N2) compounds. The recent study showed that it’s crystal structure is in the hexagonal (P6/mmm, SPG No: 191) where 1a and 1b sites partially occupied by Ba atom with 0.871 and 0.129 ratio, respectively [1]. The elastic constants and lattice dynamical properties of this compound are calculated and its stability is discussed.Item Mechanical and Vibrational Properties of ?- and ?-MgAl2Ge2 compound: Ab-initio study((WITAM-2018), 2018) Özışık, Hacı; Boğaz Özışık, Havva; Deligöz, EnginMgAl2Ge2 compound is in the hexagonal P63/mmc (?) and trigonal P-3m1 (?) structures. We have been used strass-strain method to predict the second order elastic constants (Cij) and perturbation theory for the vibrational properties of the titled compound within the density functional theory. Our results showed that the compound is satisfy mechanical stability for ?-structure confirmed by vibrational calculations. The polycrystalline aggregate behavior estimated using the Cij for mechanically stable ?-phase. They are all good agreement with available experimental theoretical data. The calculated phonon dispersion and phonon density of states are also given and discussed.Item Ab initio study of structural and mechanical properties of two dimensional Mo2ScC2(WITAM-2018, 2018) Bölen, Emre; Deligöz, Engin; Özışık, Hacı; Özışık, Havva"MXene", a new class of two dimensional materials, has attracted considerable research interest due to its outstanding physical properties as well as promising technological applications. In this work, the structural, and mechanical properties of the Monolayer Mo2ScC2 compound is calculated first time within the framework of the density-functional theory (DFT) by using the plane-wave pseudopotential approach as implemented within the VASP package. The structural parameters of Mo2ScC2 is optimized, and calculated the lattice parameters. We think that the results will guide the experimental work that is not yet done.Item Atomic and electronic structures of the group-IV elements on Si(111)-(root 3x root 3) surface(IOP Publishing, 2008) Özkaya, S.; Çakmak, M.; Alkan, B.We have examined the Si(111) surface with 1/3 monolayer of group-IV elements within the ab initio density functional theory. We have considered two possible threefoldcoordinated sites for the atom adsorption: (i) H3 site (this site is directly above a fourth-layer Si atom and (ii) T4 site (directly above a second-layer Si atom). For the atoms Ge, Sn, and Pb, the T4 position always gives the most stable configuration, comparing with the H3 site. The calculated energy difference between T4 and H3 for Pb, Ge, and Sn, is 0.32 eV, 0.59 eV, and 0.41 eV, respectively. We have also presented electronic band structure and orbital character of the surface states of the Sn/Si(111)-(? 3× ? 3) surface.Item A computational study of van der Waals tunnel transistors: Fundamental aspects and design challenges(Institute of Electrical and Electronics Engineers Inc., 2015) Cao, Jiang; Logoteta, Demetrio; Özkaya, Özkaya; Biel, Blanca; Cresti, Alessandro; Pala, Marco; Esseni, DavidWe propose a model Hamiltonian for van der Waals tunnel transistors relying on a few physical parameters that we calibrate against DFT band structure calculations. This approach allowed us to develop a fully three-dimensional (3-D) NEGF based simulator and to investigate fundamental and design aspects related to van der Waals tunnel transistors, such as: (a) area and edge tunneling components, and scaling with device area; (b) impact of top gate alignment and back-oxide thickness on the device performance; (c) influence of inelastic phonon scattering on the device operation and sub-threshold swing; (d) benchmarking of switching energy and delay. © 2015 IEEE.
