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Öğe C20 Fullerene CCl3 Adsorpsiyonunun Teorik Olarak İncelenmesi(2020) Demiray, FerhatBu çalışmada, Yoğunluk Fonksiyonel Teori (DFT) kullanılarak, C20 fullerene CCl3 (karbontriklorür) katkılanması ile elde edilen C20CCl3 molekülünün yapısal ve elektronik özellikleriincelendi. Yapılan hesaplamalarda adsorpsiyon enerjileri LDA ve GGA için sırası ile -4.17 eV ve-3.41 eV olarak elde edilmiştir. Optimize edilmiş C20CCl3 yapıda C – Cl atomları arasındaki bağuzunluklarının CCl3 moleküler yapıdaki bağ uzunluklarına göre arttığı gözlemlenmiştir. CCl3molekülünün fullerende bağlandığı karbon atomunun, fulleren yapı içinde bağ yaptığı diğerkarbon atomları ile arasındaki bağ uzunluklarının da arttığı hesaplanmıştır. CCl3 ve fullereninbirleşmesi ile elde edilen moleküler yapıda GapHL değerleri LDA ve GGA için sırası ile 0.57 ve0.73 eV olarak elde edilmiştir. C20CCl3 molekülü GapHL değerlerine göre hem LDA hemde GGAyaklaşımı için yarıiletken malzeme olarak değerlendirilebilir.Öğe CsCl (B2, Pm-3m) phase of lead chalcogenides and their ternary alloys: A computational study(Elsevier Science Sa, 2020) Demiray, Ferhat; Berber, SavaşWe report ab initio density functional theory calculations for PbX (X = S, Se, Te) compounds in the CsCl-type structure (B2, Pm-3m), and their related ternary alloys PbS1-xSex, PbS1-xTex, and PbSe1-xTex. The structural, electronic, vibrational, and optical properties have been investigated under zero and finite pressures. Our calculated lattice constant values for the binary compounds are in a reasonable agreement with previous experimental and theoretical studies. The lattice constants of ternary alloys have a linear dependence on the concentration x, indicating that the bonding character in ternary and binary alloys of lead chalcogenides are identical. We find that PbX (X = S, Se, Te) and their related ternary alloys have metallic character, and the bonding has both ionic and covalent contributions. The features in the electronic structures are closely related to the charge transfer from the Pb atom to the chalcogen, and electronegativity differences of the chalcogen atoms. Frequency-dependent dielectric functions show peculiar features to help identify the CsCl-phases by optical spectroscopy. Calculated phonon spectra indicate that both the binary compounds and the ternary alloys are dynamically stable only under pressure. A binary lead chalcogenide may be substitutionally doped by the other chalcogens up to 12% dopant concentrations.Öğe Dft study for structural and electronic properties of N2O3 adsorption onto C-20 fullerene(Springer, 2020) Demiray, FerhatStructural and electronic properties of N2O3 adsorbed on C-20 fullerene were investigated by Density Functional Theory. Before N2O3 was adsorbed on C-20 fullerene surface, the structural properties of the isomers of the N2O3 were calculated. According to the total energy calculations,asym-N2O3 is the most stable isomer since it has lower energy than the other two isomers. Data obtained for the structural properties of N(2)O(3)molecule are in agreement with the previous studies. After full structural optimization without any restrictions, the most stable structures were obtained. The adsorption energies with no dissociation of N2O3 were in the range of -2.88 to -3.55 eV for LDA and -2.02 to -2.45 eV for GGA. On the other hand, the dissociative adsorption yields a lower total energy with E-ads values of -3.72 and -2.93 eV in LDA and GGA, respectively. According to these values, adsorption can be evaluated as chemisorption for all stable structures. The adsorption occurs with no reaction barriers except for one configuration. Although the co-adsorption of NO and NO2 molecules on the same fullerene is energetically less favorable compared to their adsorptions on separate fullerenes, the dissociative co-adsorption occurs with no energy barrier. The electronic structures are dominated by charge transfer from the fullerene to the adsorbate. The obtained HOMO-LUMO gap (GapHL) values are in the range of 1.02 and 1.35 eV for both LDA and GGA, respectively. The results presented here can be expected to guide future experimental and theoretical studies as new hybrid material.Öğe Dipole moment and solvatochromism of benzoic acid liquid crystals: tuning the dipole moment and molecular orbital energies by substituted Au under external electric field(Elsevier, 2017) Sıdır, Yadigar Gülseven; Sıdır, İsa; Demiray, FerhatThe optical absorption and steady-state fluorescence spectra of 4-heptyloxybenzoic acid (4hoba), 4-octyloxybenzoic acid (400ba) and 4-nonyloxybenzoic acid (4noba) liquid crystals have been measured in a series of different polarity organic solvents. The ground state (mu(g)) and excited state (mu(e)) dipole moments of the monomeric and dimeric 4-alkyloxybenzoic acid liquid crystals have been obtained by means of different solvatochromic shift methods. HOMO-LUMO gaps (HLG) and dipole moments have been tuned by applying external electric (EF) field on monomer, dimer and Au substituted monomer and dimer liquid crystal structures. By applying external electric field, Au substituted monomer liquid crystals display semiconductor character, while Au substituted dimer liquid crystals gain metallic character under E = 0.04 V/angstrom. Eventuated specific and non-specific interactions between solvent and solute in solvent medium have been expounded by using LSER (Linear Solvation Energy Relationships). (C) 2017 Elsevier B.V. All rights reserved.Öğe Dipole moment and solvatochromism of benzoic acid liquid crystals: tuning the dipole moment and molecular orbital energies by substituted Au under external electric field (vol 1137, pg 440, 2017)(Elsevier Science Bv, 2017) Sıdır, Yadigar Gülseven; Sıdır, İsa; Demiray, FerhatThe authors regret to inform that three references in the article titled “Dipole moment and solvatochromism of benzoic acid liquid crystals: Tuning the dipole moment and molecular orbital energies by substituted Au under external electric field” are not given in the manuscript. This is purely an oversight mistake. The references are as shown in this correction. The authors would like to apologize for any inconvenience caused.Öğe Electronic structure and optical properties of Schiff base hydrazone derivatives by solution technique for optoelectronic devices: Synthesis, experiment and quantum chemical investigation(Elsevier Science Bv, 2019) Sıdır, İsa; Sıdır, Yadigar Gülseven; Berber, Halil; Demiray, FerhatIn this study, electronic, optical and spectroscopic FT-IR, UV properties of new synthesized Schiff base hydrazone derivatives, 1-(4-nitrophenyl)-2-(4-phenoxybenzylidene)hydrazone and 1-(2,4-dinitropheny1)-2-(4-phenoxybenzylidene)hydrazone are investigated by performing solution techniques and theoretical calculations. Solvatochromism and solute-solvent interactions were discussed based on the spectral results. It is observed that Schiff base hydrazone derivatives exhibit positive solvatochromism. Energy band gap E-g is determined experimentally and theoretically in solution. Concentration effect on E-g was investigated in DCM solvent for different molarities of solute. It is observed that solvent and concentration can be used for tuning E-g. NO2 substituent group gives rise to E-g value lows 0.3 eV. The refractive index (n) values were obtained from Moss, Ravindra, Herve-Vandamme, Kumar-Singh and Reddy relations based on E-g data. It is observed that n can be controlled with solvents and concentration of solutions. External electric field (EF) is theoretically applied in order to tuning HOMO-LUMO gap and dipole moment. Consequently, Schiff base hydrazone derivatives intend to be insulator under applied EF. (C) 2018 Elsevier B.V. All rights reserved.Öğe Emerging ground and excited state dipole moments and external electric field effect on electronic structure. A solvatochromism and theoretical study on 2-((phenylimino)methyl)phenol derivatives(Elsevier Science Bv, 2015) Sıdır, İsa; Sıdır, Yadigar Gülseven; Berber, Halil; Demiray, FerhatThe absorption and fluorescence spectra of three 2-((phenylimino)methyl)phenol derivatives have been evaluated in a series of organic solvents. The ground state (mu(g)) and excited state (mu(e)) dipole moments are determined by means of Lippert-Mataga, Bakhshiev, Kaski-Chamma-Viallet and Reichardt solvatochromic shift methods based on the solvent polarity parameters. Excited state dipole moments are found as larger than the ground state dipole moment due to substantial redistribution of the pi-electron density in more polar excited state and thus resonance structures of 2-((phenylimino)methyl)phenol derivatives are analyzed. Solute-solvent interactions are analyzed by means of linear solvation energy relationships (LSER) using dielectric constant function f(epsilon), refractive index function f(n) and Kamlet-Taft parameters (H-bond donor ability, alpha and H-bond acceptor ability, beta). External electric field (EF) effect on HOMO-LUMO gap (HLG) and dipole moment are investigated by B3LYP, LDA and GGA methods. Density of states (DOS) and HOMO, LUMO plots are also investigated by the same methods. (C) 2015 Elsevier B.V. All rights reserved.Öğe Estimation of ground and excited states dipole moments of alpha-hydroxy phenyl hydrazone derivatives : experimental and quantum chemical methods(Elsevier Science Bv, 2014) Sıdır, İsa; Sıdır, Yadigar Gülseven; Demiray, Ferhat; Berber, HalilThe ground state (mu(g)) and excited state (mu(e)) dipole moments of the studied alpha-hydroxy phenylhydrazones are determined by using solvatochromism theory which is based on the variation of Stokes shift with solvent's relative permittivity and refractive index. Excited state dipole moments are found as larger than the ground state dipole moment due to substantial redistribution of the pi-electron density in more polar excited state. External electric field (EF) effect on HOMO-LUMO gap (HLG) and dipole moment is studied by GGA level of theory. Density of states (DOS) and HOMO, LUMO plots are also investigated by GGA method. Solvent accessible surface (SAS) and molecular electrostatic potential (MEP) are visualized as a result of DFT calculations. (C) 2014 Elsevier B.V. All rights reserved.Öğe Investigation of structural and electronic properties of N2O4 adsorbed on C20 fullerene(Elsevier Science Sa, 2020) Demiray, FerhatWe report density functional theory calculations for structural and electronic properties of N2O4 adsorbed on C-20 fullerene. At the beginning of the study, the isomers of N2O4 molecule were obtained and their structural properties were investigated. Our total energy calculations showed that the sym-N2O4 has lower energy than the other isomers. Therefore, it was selected as the most stable isomer of all. The structural properties of N2O4 isomers determined in this study were in agreement with previous studies. Various possible adsorption geometries were taken into consideration during the adsorption process of the N2O4 molecule onto the fullerene surface. The most stable four structures were obtained without any constraints by performing full structural optimizations. The adsorption energies of these optimized stable structures were calculated as - 3.16, - 3.35, - 3.27, and - 3.18 eV for LDA and - 2.26, - 2.61, - 2.51, and - 2.27 eV for PBE. These calculated values showed that the adsorption process can be evaluated as a chemisorption. GapHL values were calculated as 1.46, 1.41, 1.21, and 1.28 eV for LDA and 1.45, 0.34, 0.86, and 1.25 eV for PBE. The results obtained in this study regarding the N2O4 adsorption onto the C-20 surfaces can be expected to guide future experimental and theoretical studies related to new hybrid semi-conductor material.Öğe INVESTIGATION ON THE ADSORPTION OF THE POTASSIUM ATOM ONTO C20 FULLERENE SURFACE(2021) Erbaş, Mehmet Dinçer; Demiray, FerhatIn this study, based on the Density Functional Theory (DFT), we examined the structural andelectronic properties of potassium (K) atoms doped fullerene (C20K).Structural optimizationcalculations were performed without any symmetry restrictions for the three distinctformations, namely, \"pentagon\", \"bridge\" and \"on-top\", in which K atom can be adsorbedonto C20 fullerene.The \"pentagon\" structure was obtained as the most stable structure becauseit has a lower total energy value compared to the other two structures.Adsorption energieswere calculated as -1.52 eV in the \"pentagon\" structure, -1.47 eV in the \"bridge\" structure and-1.41 eV in the \"on-top\" structure. According to the computed Eads values, adsorption for allof the three distinct structures is chemisorption. The GapHL value for the “pentagon”structure, which is the most stable structure, was calculated as 0.98 eV and this structure canbe considered as a semiconductor material.The results obtained by the adsorption of C20fullerene with K atom are expected to guide future experimental and theoretical studies.Öğe Structural and electronic properties of cyanide-coated fullerene C-20@(CN)(n) (n=0-20): an ab initio approach(Springer Heidelberg, 2016) Demiray, Ferhat; Sıdır, İsa; Sıdır, Yadigar GülsevenDensity functional theory calculations at the LDA level have been performed to investigate the geometrical structure, stabilities and electronic properties of cyanide-coated fullerene C-20@(CN)(n), with n = 0-20 in the ground state. From the binding energy, dissociation energy and second-order energy, even-number-coated fullerenes are more stable than odd-number ones. C-20 has been successfully coated with electron-withdrawing group CN, achieving fullerene electron acceptors which have low-LUMO levels. The lowest LUMO value obtained for C-20@(CN)(12) is -5.89 eV, which is comparable with or lower than that of C-60 and C-60@(CN)(2) fullerenes. Each of the cyanide coatings makes the fullerenes more stable with a larger HOMO-LUMO gap. Designed cyanide-coated fullerene compounds are promising and progressive to achieve a wider range of donor materials and high efficiencies in organic photovoltaic devices.Öğe Structural and electronic properties of heptachlor(Pleiades Publishing Inc, 2015) Sıdır, Yadigar Gülseven; Sıdır, İsa; Demiray, FerhatIn this work, the molecular geometry of heptachlor is investigated using ab initio HF, DFT, LDA, and GGA methods. The natural bond orbital (NBO) analysis is performed at the B3LYP/6-311++G(d,p) level of theory. The first order hyperpolarizability beta(total), the mean polarizability Delta alpha, the anisotropy of the polarizability Delta alpha, and the dipole moment mu, are calculated by B3LYP/6-311++G(d,p) and HF/6- 311++G(d,p) methods. The first order hyperpolarizability (beta(total)) is calculated based on the finite field approach. UV spectral parameters along with HOMO, LUMO energies for heptachlor are determined in vacuum and the solvent phase using HF, DFT, and TD-DFT/B3LYP methods implemented with the 6-311++G(d,p) basis set. Atomic charges and electron density of heptachlor in vacuum and ethanol are calculated using DFT/B3LYP and TD-DFT/B3LYP methods and the 6-311++G(d,p) basis set. In addition, after the frontier molecular orbitals (FMOs), the molecular electrostatic potential (MEP), the electrostatic potential (ESP), the electron density (ED), and the solvent accessible surface of heptachlor are visualized as a results of the B3LYP/6-311++G(d,p) calculation. Densities of states (DOS), the external electric field (EF) effect on the HOMO-LUMO gap, and the dipole moment are investigated by LDA and GGA methods.Öğe Theoretical investigation of structural and electronic properties of C20Li nanowire(Springer Heidelberg, 2020) Demiray, Ferhat; Berber, SavaşWe investigated electronic and structural properties of C20Li nanowire by first-principle calculations. The optimum adsorption position of Li on C-20 was found to be the bridge position by comparing the total energies of the adsorbed structures. We constructed C20Li nanowire by using Li adsorbed on C-20 at the bridge position as the building block. The nanowire has two local equilibriums at a(eq) = 7.8 and 8.4 angstrom and shows ductile behavior under mechanical stress since the system utilizes all adsorption positions to relieve the strain. The on-top adsorption is observed in over-stretched nanowires while the pentagon site is preferred in over-compressed nanowires. In view of its flexible structure, C20Li may be incorporated in a matrix without inducing strain. The system is semiconductor with energy gap values E-g < 1 eV for both aeq equilibrium lattice values. Since the highest occupied band becomes unoccupied for minority spin, spin polarization of 1 mu(B) per formula unit is observed. C20Li may be utilized as the building block of magnetic semiconductors.
