48 research outputs found
Effect of Se content on the structural, morphological and optical properties of Bi2Te3-ySey thin films electrodeposited by under potential deposition technique
No full textBi2Te3-ySey thin films with different Se contents ranging from 0.3 to 2.5 were successfully electrodeposited by under potential deposition (UPD) technique onto gold foil substrates from an electrolyte consist of Bi(NO3)(3), TeO2, and SeO2 at ambient conditions. The effects of Se content on structural, morphological and optical properties of the products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy, respectively. The XRD analysis revealed that the diffraction peaks positions of Bi2Te3-ySey thin films shifts gradually towards the higher angle side due to replacement of Te by Se atoms in the crystal structure with increasing Se content. The SEM results showed that the particle size of Bi2Te3-ySe(y) thin films decreased as the Se content increased. The optical constants of ternary Bi2Te3-ySey thin films such as refractive index, extinction coefficient, and dielectric constant were obtained from the transmission spectra in the range of 2500-10.000 nm. The direct allowed band gap energies were estimated using Tauc equation and found to increase from 0.210 to 0.282 eV with increasing Se content from 0.3 to 2.5. The dispersion behavior of refractive index was studied by the single oscillator Wemple-DiDomenico model. (C) 2016 Elsevier Ltd. All rights reserved
Theoretical studies on molecular structure and vibrational spectra of 8-hydroxyquinolinium picrate (vol 79, pg 1425, 2011)
No full textThe authors regret to inform that the oxygen atom in 8-hydroxyquinolinium was forgotten during the initial calculations and then these calculations were repeated according to the correct molecular structure. But in the above article incorrect Fig. 1, Fig. 3, Fig. 4 and Table 2, Table 4 were accidentally submitted to publication. This situation has been noticed. The correct forms of them are given as follows
Molecular structure, vibrational and chemical shift assignments of 8-hydroxy-1-methylquinolinium iodide hydrate by density functional theory (DFT) and ab initio Hartree-Fock (HF) calculations
No full textThe molecular geometry, the normal mode frequencies and corresponding vibrational assignments, (1)H and (13)C NMR chemical shift values of 8-hydroxy-1-methylquinolinium iodide monohydrate [(C(10)H(10)NO)(+)I(-)H(2)O] in the ground state were performed by HF and B3LYP levels of theory using the LanL2DZ basis set. The optimized bond lengths and bond angles are in good agreement with the X-ray data. The vibrational spectra of the title compound which is calculated by HF and DFT methods, reproduces vibrational wave numbers and intensities with an accuracy which allows reliable vibrational assignments. The title compound [(C(10)H(10)NO)(+)I(-)H(2)O] have been studied theoretically in the 4000-200 cm(-1) region and the assignment of all the observed bands were made. The analysis of the infrared spectra indicates that there are some structure-spectra correlations. These methods are proposed as a tool to be applied in the structural characterization of 8-hydroxy-1-methylquinolinium iodide monohydrate [(C(10)H(10)NO)(+)I(-)H(2)O], and thus providing useful support in the interpretation of experimental NMR data. (C) 2008 Elsevier B.V. All rights reserved
Effects of Different Basis Sets and Donor-Acceptor Groups on Linear and Second-Order Nonlinear Optical Properties and Molecular Frontier Orbital Energies
No full textThe calculation of molecular hyperpolarizability, molecular frontier orbital energies of some donor-acceptor oxadiazoles (5a-f, 8a-f, and 9a-f) have been investigated using ab initio methods and different basis sets. Ab initio optimizations were performed at the Hartree-Fock (HF) and density functional (Beckee-3-Lee-Yang-Parr; B3LYP) levels of theory with 6-31G basis set. The polarizability (), anisotropy of polarizability (Delta alpha), and ground-state dipole moment (mu), first hyperpolarizability (beta), and molecular frontier orbital (HOMO, highest occupied molecular orbital and LUMO, lowest unoccupied molecular orbital) energies of 5a-f, 8a-f, and 9a-f have been calculated at the HF and B3LYP methods with 6-31G, 6-31G(d), 6-31+G(d), 631++G(d,p), 6-311G, 6-311G(d), 6-311+G(d), and 6-311++G(d,p) basis sets. Also, the molecular hardness (eta) and electronegativity (chi) parameters have been obtained using molecular frontier orbital energies. The , Delta alpha, mu, beta, HOMO, LUMO energies, eta and chi parameters have been investigated as dependence on the choice of method and basis set. The variation graphics of , Delta alpha, mu, beta, eta, and chi parameters using HF and B3LYP methods with different basis sets are presented. We have examined the frontier molecular orbital pictures of 5a-f, 8a-f, and 9a-f using B3LYP/6-31++G(d,p) level. The 5a-f, 8a-f, and 9a-f display significant linear, second-order molecular nonlinearity, and molecular parameters and provide the basis for future design of efficient nonlinear optical materials having the 1,3,4-oxadiazole core. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 130-147, 2011https://doi.org/10.1002/qua.2241
Molecular structure, IR and NMR spectra of 2,6 distyrylpyridine by density functional theory and ab initio Hartree-Fock calculations
No full textVibrational frequencies and gauge including atomic orbital (GIAO) C-13 NMR and H-1 NMR chemical shift values of 2,6 distyrylpyridine (C21H17N) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. These methods are proposed as a tool to be applied in the structural characterization of 2,6 distyrylpyfidine (C21H17N). The title compound has C-2 nu point group, thus providing useful support in the interpretation of experimental IR data. In addition, obtained results were related to the linear correlation plot of experimental C-13 NMR, H-1 NMR chemical shifts values and IR data. (C) 2007 Elsevier B.V. All rights reserved
Theoretical studies of molecular structure and vibrational spectra of glutaconic acid
No full textThe molecular geometry and vibrational frequencies of glutaonic acid (C5O4H6) in the ground state has been calculated using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths and bond angles obtained by using HF and DFT (B3LYP) show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of glutaconic acid and calculated results by density functional B3LYP and Hartree-Fock methods indicate that B3LYP is superior to the scaled Hartree-Fock approach for molecular vibrational problems. (c) 2005 Elsevier B.V. All rights reserved
Density Functional Theory and ab initio Hartree-Fock Calculations of Molecular Structure and Vibrational Spectra of Anilinium Nitrate
No full textThe molecular geometry, vibrational frequencies, infrared intensities, Raman scattering activities and several thermodynamic parameters of anilinium nitrate in the ground state have been calculated by both Hartree-Fock (HF) and three density functional theory (DFT) methods (B3LYP, BLYP and B3PW91) using the 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray structure. The optimized geometric bond lengths are described very well by the HF method while bond angles are reproduced more accurately by the DFT methods. Comparison between the observed fundamental vibrational frequencies of anilinium nitrate and the results of DFT and HF methods indicates that B3LYP is Superior to the scaled HF, BLYP and B3PW91 approaches for molecular vibrational problems. The computed vibrational frequencies are used to determine the types Of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data
Ab initio HF and DFT calculations on an organic non-linear optical material
No full textThe molecular geometric optimization, vibrational frequencies, and gauge-including atomic orbital (GIAO) (1)H and (13)C chemical shift values of 3-[(1E)-N-ethylethanimidoyl]-4-hydroxy-6-methyl-2H-pyran-2-one have been investigated by using ab initio Hartree-Fock (HF) and density functional method (B3LYP: Becke-3-Lee-Yang-Parr) with 6-31G(d) and 6-31++G(d,p) basis sets. Also, the first hyperpolarizabilities have been calculated at the HF and B3LYP levels employing the corresponding basis sets. To understand this phenomenon in the context of molecular orbital picture, we examined the molecular HOMOs and molecular LUMOs generated via HF and B3LYP levels. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Data of 3-[(1E)-N-ethylethanimidoyl]-4-hydroxy-6-methyl-2H-pyran-2-one display significant second-order molecular nonlinearity and provide the basis for design of efficient nonlinear optical materials
Linear and non-linear optical properties of some donor-acceptor oxadiazoles by ab initio Hartree-Fock calculations
No full textThe molecular hyperpolarizability of some donor-acceptor oxadiazoles was investigated using ab initio methods. Ab initio optimizations were performed at the Hartree-Fock level using different basis sets, starting with the minimal basis set, and then split valence sets. The first hyperpolarizabilities were calculated at the Hartree-Fock level employing the corresponding basis sets using Gaussian 98W. In general, the first hyperpolarizability is dependent on the choice of method and basis set. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular HOMOs and molecular LUMOs generated via HF/6-31G level. It has also been calculated the polarizability, anisotropy of polarizability and ground state dipole moment of all the molecules. Several of these oxadiazoles display significant second-order molecular nonlinearity, beta(8.57-195.05 x 10(-30) esu) and provide the basis for future design of efficient nonlinear optical materials having the oxadiazole core
Theoretical investigation of superconductivity in SrAuSi3 and SrAu2Si2
No full textThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Available online 8 April 2016The structural and electronic properties of BaNiSn3-type SrAuSi3 and ThCr2Si2-type SrAu2Si2 have been investigated by using the planewave pseudopotential method and the density functional theory. The electronic structures and phonon dispersion relations of these two materials have been analyzed with and without the inclusion of spin-orbit interaction, and similarities and differences highlighted. By integrating the Eliashberg spectral function α2F(ω), the average electron-phonon coupling parameter is determined to be λ=0.47 for SrAuSi3 and 0.42 for SrAu2Si2. The largest contribution to the electron-phonon coupling for SrAuSi3 comes from the Si p electrons near the Fermi energy and Si-related vibrations. Using a reasonable value of μ∗=0.12 for the effective Coulomb repulsion parameter, the superconducting critical temperature Tc for SrAuSi3 is found to be 1.47 K which compares very well with its experimental value of 1.54 K.This work was supported by the Scientific and Technical Research Council of Turkey (TÜBİTAK) (Project no. MFAG-115F135)
