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    Molecular structure and spectral investigations of 3,5-Di-tert-butyl-o-benzoquinone
    (Elsevier, 2017) Yilmaz, M.; Aydin, B.; Dogan, O.; Dereli, O.
    Conformational analysis of 3,5-Di-tert-butyl-o-benzoquinone molecule was performed and two stable conformers were determined by B3LYP/6-311++G(d,p). Using the most stable one, molecular structural parameters, vibrational frequencies were calculated by B3LYP/6-311++G(d,p), B3LYP/6-31G(d) and BLYP/6-31G(d,p) levels of theory. The FT-IR spectrum of the compound was recorded in the region 4000-550 cm(-1). The Raman spectrum was also recorded in the region 3500-100 cm(-1). Calculated results were compared with experimental counterparts. The best results were obtained from B3LYP/6-311++G(d,p) calculations. Experimental C-13 and H-1 NMR data of tittle compound were taken from literature and the calculated results compared with these data. Vibrational and NMR band assignments were performed. HOMO-LUMO energies, molecular electrostatic potentials and thermodynamic properties were also given for further investigations of our structure. (C) 2016 Elsevier B.V. All rights reserved.
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    Structural and superconducting properties in Y0.6Gd0.4Ba2(Nb)Cu3O7-y cuprates doped with niobium
    (Elsevier Science Bv, 2012) Yilmaz, M.; Dogan, O.
    Polycrystalline YBa2Cu3O7-y (YBCO) and Y0.6Gd0.4Ba2-xNbxCu3O7-y (YGBNCO) compounds with 0 <= x <= 0.225 were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray difference (XRD) and scanning electron microscopy (SEM). The transport properties were measured by the (FPP) method in the temperature range from 70 to 130 K. As the Nb content in the samples increased, a diffused phase indicating a niobium perovskite phase and a small amount of unidentified phase appeared. With the increase of Nb content, the superconducting transition temperature T-c(onset) increased slowly with x <= 0.125, and then it remained unchanged or slowly decreased with 0.125 <= x <= 0.225. It could be found that there was a slow decrease of zero-resistance temperature, T-c(offset), with the increase of Nb content. The larger transition width might result from the YBa2NbO6 phase, impurity and unidentified phases of the sample due to the Nb doping.