21 results
Search Results
Now showing 1 - 10 of 21
Publication Metadata only Structure and Vibrational Spectra of Benzidine(Elsevier, 2003-06-01) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127The geometry and vibrational spectrum of benzidine have been computed by ab initio calculations using the DFT/B3LYP method with 6-31+G(d,p) basis set. In the most stable geometry, the dihedral angle between the two phenyl rings was found to be around 38°. Calculated wavenumbers were scaled by a single factor 0.965 to approximately correct for vibrational anharmonicity as well as for overestimation of the force constants. Normal coordinate analysis of benzidine and some of its deuterated derivatives have also been performed in valance force field approximation in order to demonstrate the transferability of the force field of aniline. Good agreements between the two different calculation results (ab initio and force field refinement methods) and between the calculated and observed values are found.Publication Metadata only Structure and Vibrational Analysis of 5-Chlorouracil and its Dimers(2018) Akalın, Elif; Çelik, Sefa; AKYÜZ, SEVİM; 46357; 110147; 10127Publication Metadata only Anharmonic DFT study of the vibrational wavenumbers of 5-Chlorouracil(2017) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127Publication Embargo Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures(Springer, 233 Spring St, New York, Ny 10013 Usa, 2012-11-28) Erol, Ayşe; Akalın, Elif; Sarcan, Fahrettin; Dönmez, Ömer; Arıkan, Mehmet Çetin; Puustinen, Janne; Guina, Mircea; AKYÜZ, SEVİM; TR54563; TR1362; TR108291; TR46357; TR150431; TR10127The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga1 -aEuro parts per thousand x In (x) N (y) As1 -aEuro parts per thousand y /GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.Publication Metadata only Interaction Of Isoniazid With Al(OH)(3): A DFT Study(Asian Journal Of Chemistry, 11/100 Rajendra Nagar, Sector 3,, Sahibabad 201 005, Ghaziabad, india, 2010-05) Akalın, Elif; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR111424; TR10127; TR46357The harmonic and anharmonic vibrational wavenumbers of isoniazid (INH) interacting with Al(OH), through the ring nitrogen have been calculated by using the density functional theory (DFT) method with Becke3Lyp functional and 6-31++G(d,p) basis set, in order to investigate coordination through the ring nitrogen effects on INH vibrational wavenumbers The total energy distributions (TED) of the vibrational modes were calculated by using scaled quantum mechanical (SQM) analysis Fundamentals were characterized by their total energy distributions Coordination sensitive modes of isoniazid were determined.Publication Metadata only Investigation of Adsorption of 5-Fluorouracil and 5-Bromouracil onto Sepiolite and Loughlinite: An IR Spectroscopic Study(Asian Journal Of Chemistry, 11/100 Rajendra Nagar, Sector 3,, Sahibabad 201 005, Ghaziabad, India, 2014-08) Akalın, Elif; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; 10127; 46357The adsorption of 5-fluorouracil (5FU) and 5-bromouracil (5BrU) by sepiolite and loughlinite (natural Na-sepiolite) has been investigated using FT-IR spectrometry. The spectroscopic results indicate that 5-halogenouracils adsorbed on sepiolite and loughlinite are coordinated to surface hydroxyls and/or to Lewis acidic centers by hydrogen bonding interaction through the oxygen lone pairs. Some intensity and frequency changes in the OH stretching and deformation bands of surface hydroxyls (Si-OH) of the 5-fluorouracil and 5-bromouracil treated sepiolite and loughlinite were observed. Adsorption capacity of the sepiolite is found to be higher than loughlinite for 5-halogenuracils. Moreover adsorption capacity of clays were found to decrease in the order 5-fluorouracil >5-bromouracil.Publication Metadata only Vibrational study on Zn(Pyrimidine)(2)Cl-2, Pyrimidine-Al(OH)(3) and Pyrimidine-(Al(OH)(3))(2) complexes(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2008-11-20) Akalın, Elif; AKYÜZ, SEVİM; TR10127; TR46357A molecular modeling analysis was performed via density functional theory (DFT), using B3LYP/6-31++G(d,p) basis set on Zn(PM)(2)Cl-2, PMAI(OH)(3) and PM-(AI(OH)(3))(2) complexes (PM: Pyrimidine) in order to investigate monodentate and bidentate coordination effects on pyrimidine vibrational wavenumbers. The Zn(PM)(2)Cl-2. Complex was synthesized and the FT-IR and FT-Ra spectra were recorded which, when compared to the calculated wavenumbcrs of the model mono- and bidentate Al(OH)(3) Complexes, showed that pyrimidine behaved as a rnonodentate ligand. Anharmonic corrections to the calculated wavenumbers of the Zn(PM)(2)Cl-2 complex were done and the results led to a good overall agreement with the observed wavenurnbers. A complete assignment of the fundamentals was proposed based on the internal mode analysis done by Gaussian03 programme. (C) 2007 Elsevier B.V. All rights reserved.Publication Metadata only Experimental And Theoretical Vibrational Spectroscopic Investigation Of Zn(II) Halide Complexes Of 3-Aminopyridine And 3-Chloropyridine(Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands, 2011-05-03) Akalın, Elif; AKYÜZ, SEVİM; TR10127; TR46357The aim of this study is to analyse the influence of the formation of metal-ligand bond through the ring nitrogen on the vibrational wavenumbers of pyridine derivatives, depending on the electron releasing (NH2) or electron withdrawing (CI) substituent, in the same position. As pyridine derivatives, 3-aminopyridine (3apy) and 3-chloropyridine (3Clpy) were used. Moreover, determination of the wavenumbers of metal-ligand bond vibrations has a separate interest. In order to investigate the influence of the counter ligand, halide, on pyridine derivative vibrations, calculations were carried out on both Zn(L)(2)Cl(2)and Zn(L)(2)Br-2 (where L = 3-aminopyridine or 3-chloropyridine) compounds. Full assignment of the spectra is proposed and the analysis of the experimental data are supported by DFT calculations performed with B3LYP functional and the 6-311++G(d,p) basis set. The FT-IR (400-4000 cm(-1)) and Raman (100-3200 cm(-1)) spectra of compounds are recorded and are compared with that of the calculated spectra. Anharmonic corrections to the harmonic wavenumbers are done with the same method and level of theory. The coordination effects on vibrational wavenumbers of 3apy and 3Clpy were discussed by comparing the spectra of free and coordinated molecules. (C) 2011 Elsevier B.V. All rights reserved.Publication Metadata only Ab Initio and Raman Study of Medium Range Ordering in GeSe2 Glass(Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands, 2013-08-01) Akalın, Elif; Holomb, R.; Mitsa, V.; Sichka, M.; AKYÜZ, SEVİM; 10127; 46357High resolution Raman spectra of GeSe2 glass were measured and fitted using individual Gaussian components. The structural origin of the components were interpreted using the results of ab initio density functional theory calculations performed on GenSem nanoclusters (n = 2-6, 12; m = 6-9, 12, 14-16, 30) which represent the local structure of GeSe2 glass and on some "defect" GenSem clusters that are thought to be related to the inhomogeneity of the structure at the nanoscale. The calculated vibrational properties of GenSem nanoclusters and their couplings with the short- and medium-range order structure formations in GeSe2 glass are analyzed and discussed. (c) 2013 Elsevier B.V. All rights reserved.Publication Metadata only FT-IR and Raman Spectroscopic And DFT Theoretical Investigations On Zn(II) Halide Complexes Of 2-Aminopyrimidine(Elsevier Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlands, 2010-03-26) Akalın, Elif; AKYÜZ, SEVİM; TR46357; TR10127In this study the vibrational spectra of monomeric Zn(L)(2)X(2) (X = Cl and Br; L = C(4)H(5)N(3) = 2APM, 2-aminopyrimidine) compounds are reported and discussed. Full assignment of the spectra is presented and the analysis of the experimental data is supported by DFT calculations performed with B3LYP functional and the 6-311++G(d,p) basis set. The FT-IR (400-4000 cm(-1)) and Raman (100-3200 cm(-1)) spectra of compounds are recorded and compared with that of the calculated spectra. Anharmonic corrections to the harmonic wavenumbers are done with the same method and level of theory. The coordination effects on vibrational wavenumbers of 2APM are discussed in detail by comparing the spectra of free and coordinated 2APMs. The geometry optimization of [Zn(L)(2)X(2)] calculated using the DFT/B3LYP method with a 6-311++G(d,p) basis set yields a slightly distorted tetrahedral environment around Zn ion and compound reveals the C2 symmetry. The 2APM ligand is coordinated to Zn atom via ring nitrogen atom as monodentate ligand. The computed C-N bond length in Zn(2APM)(2)Br(2) complex is found to be slightly longer than the corresponding bond length in Zn(2APM)(2)Cl(2) complex. (C) 2010 Elsevier B.V. All rights reserved.
- «
- 1 (current)
- 2
- 3
- »