Mustafa Akdogan

Ab initio Hartree-Fock and density functional theory study on characterization of 3-(5-methylthiazol-2-yldiazenyl)-2-phenyl-1H-indole

The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties, UV-vis spectra and atomic charges of 3-(5-methylthiazol-2-yldiazenyl)-2-phenyl-1H-indole molecule have been investigated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods at 6-31G (d,p) basis set. The obtained bond lengths and bond angles have been seen to be good agreement with the experimental data. After calculated vibrational frequencies have been compared with each other, the correlation coefficient has been determined. Moreover, we have not only simulated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) but also determined the transition state and energy band gap. Infrared intensities and Raman activities have been also reported.

Density functional theory study on the identification of 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol

This study deals with the identification of a title compound, 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol by means of quantum chemical calculations. The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments, thermodynamic properties, charge analyses, nuclear magnetic resonance (NMR) chemical shifts and ultraviolet-visible (UV-vis) spectra of the title molecule in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra of the title compound were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the obtained optimized geometric parameters (bond lengths, bond angles and bond dihedrals) and vibrational frequencies were observed to be in good agreement with the available experimental results. Moreover, the calculations of the electronic spectra, (13)C and (1)H chemical shifts were compared with the experimental ones. Furthermore, we not only simulated the frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition states and energy band gaps, as well. It was found that charge analyses supported the evidences of MEP. Infrared intensities and Raman activities were also reported.

Experimental and theoretical studies on the identification of p-biphenyloxycarbonylphenyl acrylate

This study presents the identification of a title compound, p-biphenyloxycarbonylphenyl acrylate by means of experimental and theoretical evidences. The spectroscopic properties of the compound were experimentally investigated by Fourier transformation-infrared spectra (in the region 400-4000 cm(-1)) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz). Moreover, the optimized molecular structures, vibrational frequencies including infrared intensities and Raman activities, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, thermodynamic properties, atomic charges and ultraviolet-visible (UV-vis) spectra were analyzed utilizing ab initio Hartree-Fock (HF) and Density Functional Theory (B3LYP) methods at 6-31G(d,p) calculation level. It was found that the vibrational frequencies and chemical shifts obtained were shown to have a good agreement with available experimental results. We not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also evaluated the transition state and energy band gap clearly.

First-principles calculations on vibrational and dielectric properties of chalcopyrite CuGaS2

We have performed a first-principles study of structural, dynamical and dielectric properties of chalcopyrite semiconductor CuGaS2. The calculations have been carried out within the local density functional approximation using norm-conserving pseudopotentials and a plane-wave basis. Born effective charge tensors, dielectric permittivity tensors, the phonon frequencies at the Brillouin zone centre and mode oscillator strengths are calculated using density functional perturbation theory. The calculated properties help resolve the source of some of the discrepancies in the experimental literature.

Influence of gold diffusion-doped on phase formation, superconducting and microstructure properties of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconductors

We report on low-field magnetic properties of gold diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy superconducting bulk samples by performing ac susceptibility measurements. The undoped samples were prepared by the standard solid-state reaction method. Doping of Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was carried out by means of Au-diffusion during sintering from an evaporated gold film on pellets. To investigate the effect of gold-diffusion and diffusion-annealing duration on transport, magnetic and microstructure properties of the superconducting samples we performed magnetoresistivity, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The ac susceptibility as a function of temperature measurements were carried out at different values of the ac magnetic field amplitudes (Hac) in the range between 20A/m and 320 A/m for 211 Hz. The imaginary part of ac susceptibility measurements is used to calculate intergranular critical current density Jc(Tp) using the Bean Model. Jc(Tp) is seen to increase from 60 A cm-2 to 90 A cm-2 with increasing diffusion-annealing time from 10 h to 50 h. The peak temperature, Tp, in the imaginary part of the ac susceptibility is shifted to a lower temperature with decreasing diffusion-annealing duration as well as increasing ac magnetic fields. The force pinning density (αjj (0)) increased with increasing diffusion annealing time. The value of Tc in gold-diffused samples, in comparison with the undoped samples, increased from 100 ± 0.2 K to 104 ± 0.2 K. It was observed that the value of Tc-offset of the gold-doped samples enhanced with further increasing diffusion-annealing duration. XRD patterns and SEM micrographs are used to obtain information about Bi-2223 phase ratio, lattice parameters and grain size of the samples. Gold doping enhanced the formation high-Tc phase and increased the grain size. The possible reasons for the observed improvements in transport, microstructure and magnetic properties due to Au diffusion and diffusion-annealing time were discussed.

Design, Fabrication, and Testing of MgB2/Fe Racetrack Coils

We fabricated four superconducting racetrack coils wound by bare <italic>in situ</italic> MgB₂/Fe mono and multifilamentary wires produced in our laboratory by using the wind-and-react method. Transport measurements in self-field were performed in a liquid helium dewar. The magnetic field flux density <italic>B</italic> = 25 mT for <italic>I</italic> = 92 A was measured to verify how the current flowed inside the coil for one of the coils by means of a cryogenic axial Hall sensor placed into the central bore region of the coil. The coil with 36 turns wound by mono MgB₂/Fe wire of <italic>l</italic> = 24 m has a highest current-carrying capacity of more than 150 A at <italic>T</italic> = 4.2 K and self-field among the coils. The coils fabricated by multifilamentary wires have relatively low engineering critical current values of <italic>I</italic>_ce = 67 A for 18 + 1 and <italic>I</italic>_ce = 57 A for 4 + 5 superconducting/copper filament wires at <italic>T</italic> = 4.2 K in self-field. Our results form essential contribution toward determination of the possible use of low-cost MgB₂/Fe wires in low-field superconductor coil applications.