Fizik Bölümü / Department of Physics
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Browsing Fizik Bölümü / Department of Physics by Author "Akalın, Elif"
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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 Adsorption and Interaction of 5-fluorouracil with Montmorillonite and Saponite by FT-IR Spectroscopy(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2007-05-27) Akalın, Elif; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR46357; TR111424; TR10127Adsorption of 5-fluorouracil (5-FU) on montmorillonite and saponite has been investigated using FT-IR spectrometry. The intercalation of 5-FU within montmorillonite or saponite has been shown by X-ray diffraction to increase the interlayer spacing. In order to investigate interaction of 5-FU with clays, the harmonic and anharmonic vibrational wavenumbers of free 5-FU and 5-FU interacting with AI(OH)3 have been calculated at the DFT/B3LYP level with 6-31 ++G(d,p) basis set by using Gaussian 03 program set. The solution effect on 5-FU was also calculated by using polarizable continuum model (PCM). Experimental and calculated results indicated that 5-FU interacted with clays by direct or indirect coordination (through water molecules) to the Lewis acidic centers. (C) 2006 Elsevier B.V. All rights reserved.Publication Metadata only Adsorption Of Isoniazid Onto Sepiolite-Palygorskite Group Of Clays: An IR Study(Pergamon-Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1Gb, England, 2010-04) Akalın, Elif; AKYÜZ, SEVİM; AKYÜZ, ZEKİ TANIL; TR10127; TR111424; TR46357The adsorption of isoniazid (INH) on sepiolite, loughlinite (natural Na-sepiolite) and palygorskite from Anatolia was investigated by FT-IR spectroscopy. Experimental results indicated that INH molecules, adsorbed on sepiolite-palygorskite group of clays, are coordinated to surface hydroxyls by H-bonding interaction through the pyridine ring nitrogen lone pairs. Moreover, some of the adsorbed INH molecules may enter the interior channels of the sepiolite-palygorskite structure and involve H-bonding interaction with zeolitic water. Some intensity and frequency changes in the OH stretching band of surface hydroxyls (Si-OH) of the INH-treated sepiolite and loughlinite were observed. However, this band is found to be less affected by the adsorption of isoniazid in the case of palygorskite, probably because the surface Si-OH groups in palygorskite appear to be less abundant than in sepiolite or loughlinite. (C) 2010 Elsevier B.V. All rights reserved.Publication Metadata only Anharmonic DFT study of the vibrational wavenumbers of 5-Chlorouracil(2017) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127Publication Metadata only Calculation and analysis of IR spectrum of 2-aminopyridine(Elsevier, 1999-05-25) Akalın, Elif; Büyükmurat, Y.; Özel, Ayşen E.; AKYÜZ, SEVİM; 46357; 110745; 10127Normal coordinate analysis of 2-aminopyridine (2AP) and ND2-pyridine have been performed in valance force field approximation. 2AP was taken as planar because of the low barrier to amino group inversion. The IR absorption intensities have been calculated and the electro–optical parameters (EOP) were fitted to experimental data in order to produce the experimental relative intensities. The created force field and EOP reproduce the IR spectrum of the molecule studied well.Publication 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 Experimental and theoretical study of the vibrational spectra of paraphenylenediamine transition metal (II) complexes(Elsevier, 2001-05-28) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127The effect of coordination of p-phenylenediamine molecule (PPD) to a transition metal has been investigated by making use of the normal coordinate analysis. The reliable force field of coordinated PPD have been determined by refinement of the free PPD in order to fit the experimental wavenumbers of transition metal (II) PPD complexes. Additionally, CdI2(PPD) and MnCl2(PPD) complexes have been prepared and their vibrational assignment is provided based on this calculation.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 Force field and IR intensity calculations of aniline and transition metal(II) aniline complexes(Elsevier, 1999-05-25) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127A complete interpretation of the vibrational spectrum of aniline was carried out on the basis of normal coordinate analysis. The reliable force field and electro-optical parameters of aniline was determined by refinement in order to fit in the calculated wavenumbers and intensities of NH2- and ND2-aniline molecules with the experimental values. The geometrical parameters of free aniline were taken from experimental results. The initial force field parameters of aniline were refined from the corresponding parameters of benzene molecule. The initial values of bond dipole moments of the molecule were calculated by PM3 method. The force field of transition metal (II) aniline complex was determined by refinement of aniline force field. Coordination effect on aniline modes are interpreted in terms of changes in hybridization about the nitrogen atom.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.Publication Metadata only Infrared and Raman spectroscopic study of 4-aminopyrimidine tetracyanonickelate complexes(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2007-05-27) Akkaya, Yasemin; Akalın, Elif; AKYÜZ, ZEKİ TANIL; AKYÜZ, SEVİM; TR111424; TR10127; TR175409; TR463574-Aminopyrimidine tetracyanonickelate, M(4APM)(2)Ni(CN)(4) {where M = Mn, Co, Ni, Zn or Cd; 4APM = 4-aminopyrimidine}, coordination polymer compounds have been prepared for the first time and their FT-IR (400-4000 cm(-1)) and FT-Raman (704000 cm(-1)) spectra are reported. 4APM is coordinated to M(II) through one of the pyrimidine ring nitrogen atoms as a monodentate ligand; the amino group is not involved in the complex formation. Vibrational bands arising from both 4APM and the Ni(CN)(4) group, were assigned. The effect of coordination on 4APM vibrational wavenumbers is analysed by comparison with isostructural compounds. (C) 2006 Elsevier B.V. All rights reserved.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 New Ring-Like Models and ab Initio DFT Study of the Medium-Range Structures, Energy and Electronic Properties of GeSe2 Glass(Taylor & Francis Ltd, 4 Park Square, Milton Park, Abingdon Ox14 4Rn, Oxon, England, 2013-07-01) Akalın, Elif; Holomb, R.; Mitsa, V.; AKYÜZ, SEVİM; 46357; 10127Ab initio DFT calculations were performed on GenSem nanoclusters (n=2, 3, 5, 6, 12; m=6-9, 14, 16, 30) that 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 optimal geometries, total energies and their derivatives as well as the electronic properties of GenSem nanoclusters were calculated using traditional DFT method. In addition, the TD-DFT method has been applied to calculate the electronic band gaps of the clusters. The calculated physico-chemical properties of GenSem nanoclusters and their couplings with the local-and medium-range order structure formations in GeSe2 glass are analysed and discussed.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 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 Theoretical Studies of Molecular Structure and Vibrational Spectra of Free and Hydrogen Bonded Complexes of Free Sulfanilamide(2006) Akalın, Elif; Özel, Ayşen; AKYÜZ, SEVİM; ILDIZ, GÜLCE ÖĞRÜÇ; 107326; 46357; 110745; 10127Publication Metadata only Vibrational Analysis of Free and Hydrogen Bonded Complexes of Nicotinamide and Picolinamide(Elsevier, 2006-11-24) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127Harmonic and anharmonic vibrations of free nicotinamide (NIA) and picolinamide (PIA) molecules together with their hydrogen bonded complexes H2O–NIA and H2O–PIA have been studied by means of density functional method. The calculation results of the vibrational spectra of free molecules have been investigated and are compared to the available experimental spectra. The vibrational wavenumbers of both molecules have also been calculated by polarizable continuum model (PCM) that represents the solvent as a polarizable continuum and places the solute in a cavity within the solvent (water is chosen as the solvent in this study). The results of PCM calculations and the H2O–NIA, H2O–PIA complexes, are used to investigate the H-bonding interactions of both molecules with the water molecule. The harmonic wavenumbers have been scaled by proper factors obtained by comparing the observed versus calculated wavenumbers and it is shown that anharmonic corrections on the vibrational spectra provided a better agreement between the observed and calculated wavenumbers compared to the results obtained by scaling factor method.Publication Metadata only Vibrational analysis of isonicotinamide(Elsevier, 2005-06-03) Akalın, Elif; Yılmaz, A.; AKYÜZ, SEVİM; 46357; 10127The FT-IR and FT-Raman spectra of isonicotinamide (in solid phase) have been recorded in the regions 4000–400 and 4000–70 cm−1, respectively. The geometry optimizations and vibrational spectrum calculations of isonicotinamide have been carried out at the DFT/B3LYP level with 6-31++G(d,p) basis set. With the SQM approach, the force field of isonicotinamide obtained by DFT calculations has been corrected by a set of scaling factors to get a good agreement between observed and calculated wavenumbers. Isonicotinamide interacting with Al(OH)3 has also been studied by B3LYP/6-31++G(d,p) calculations and the SQM results of both molecules have been compared to investigate how the coordination through the ring nitrogen effects the isonicotinamide vibrational wavenumbers.Publication Metadata only Vibrational structure of free and hydrogen bonded complexes of isoniazid: FT-IR, FT-Raman and DFT study(Elsevier, 2007-05-27) Akalın, Elif; AKYÜZ, SEVİM; 46357; 10127The combined experimental and theoretical study on molecular vibrations of isoniazid (INH) were reported by using density functional (DFT) method to determine the geometric and vibrational characteristics of INH with the B3LYP/6-31++G(d,p) basis set. Anharmonic corrections to the wavenumbers were done and the results led to a good overall agreement with the observed wavenumbers. A complete assignment of the fundamentals was proposed based on the total energy distribution (TED) calculation. The calculated harmonic wavenumbers were also scaled by a single scaling factor (0.974) however the calculated anharmonic wavenumbers were shown to be superior to the scaled wavenumbers in being much closer to the observed wavenumbers in amount. To investigate the hydrogen bonding interactions of INH, hydrogen bonded complexes of the molecule (H2OINH) were studied, again using DFT method with B3LYP/6-31++G(d,p) basis set both at harmonic and anharmonic levels. To see the solvent effect on the free INH molecule, another calculation was done using DFT/B3LYP/6-31++G(d,p) in connection with PCM (Polarizable Continuum Model – water chosen as the solvent).