Erdoğan Tarcan

Molecular structure and vibrational assignment of melaminium phthalate by density functional theory (DFT) and ab initio Hartree-Fock (HF) calculations.

The molecular geometry, the normal mode frequencies and corresponding vibrational assignment of melaminium phthalate (C3H7N6+.C8H5O4(-)) in the ground state were performed by HF and B3LYP levels of theory using the 6-31G(d) basis set. The optimized bond length numbers with bond angles are in good agreement with the X-ray data. The vibrational spectra of melaminium phthalate which is calculated by HF and B3LYP methods, reproduces vibrational wave numbers with an accuracy which allows reliable vibrational assignments. The title compound has been studied in the 4000-100 cm(-1) region where the theoretical evaluation and assignment of all observed bands were made.

Quantum chemical computational studies on bis-thiourea zinc acetate

In this study, quantum chemical calculations of vibrational spectra, Raman spectra, electronic properties (total energy, dipole moment, electronegativity, chemical hardness and softness), Mulliken atomic charges and thermodynamic parameters of bis-thiourea zinc acetate (BTZA) have been performed using Gaussian 09 program. Additionally, nonlinear optical (NLO), conformational, natural bond orbital (NBO) analyses of BTZA have been carried out using the same program. The structural and spectroscopic data of the molecule in the ground state have been calculated using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with the 6-311++G(d,p) basis set. In addition, the molecular frontier orbital energies (HOMO, HOMO-1, LUMO and LUMO+1) of the title compound have been calculated at the HF and B3LYP levels. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally, the calculated results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with the experimental ones.

Theoretical investigations on nonlinear optical and spectroscopic properties of 6-(3,3,4,4,4-pentafluoro-2-hydroxy-1-butenyl)-2,4-pyrimidinedione: An efficient NLO material

In this study, quantum chemical calculations of geometric parameters, conformational, natural bond orbital (NBO) and nonlinear optical (NLO) properties, vibrational frequencies, 1H and 13C NMR chemical shifts of the title molecule [C9H7F5N2O3] in the ground state have been calculated with the help of Density Functional Theory (DFT-B3LYP/6-311++G(d,p)) and Hartree-Fock (HF/6-311++G(d,p)) methods. The optimized geometric parameters, vibrational frequencies, 1H and 13C NMR chemical shifts values are compared with experimental values of the investigated molecules. Comparison between experimental and theoretical results showed that B3LYP/6-311++G(d,p) method is able to provide more satisfactory results. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular frontier orbital energies (HOMO, HOMO-1, LUMO, and LUMO + 1), the energy difference (ΔE) between EHOMO and ELUMO, electronegativity (χ), hardness (η), softness (S) calculated by HF/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The molecular surfaces, Mulliken, NBO, and Atomic polar tensor (APT) charges of the investigated molecule have also been calculated by using the same methods.

Structural and Dielectric Properties of Polythiophene/Chrom(III) Acetylacetonate Composites

The dielectric and morphological properties of polythiophene (PT) filled with various mass fractions of chrom(III) acetylacetonate (Cr(acac)3), synthesized via chemical oxidative polymerization, are described. Significant shifts of the absorption peak of the C-S bond in the Fourier transform infrared (FT-IR) spectra indicated that the metal cations mostly interacted with sulfur atoms. Thermal analyses performed by differential scanning calorimetry (DSC) indicated that the cold crystallization temperature (Tcc) of PT decreased with increasing doping level. Microstructural differences were observed between PT and its composites in scanning electron microscopy (SEM) images. Dielectric measurements showed that the conductivity of the PT significantly increased with increasing doping level, from ˜10−7 S/m to ˜10−4 S/m at 10 kHz and 300 K.

THE ADSORPTION OF ANIONIC AND CATIONIC SURFACTANTS BY THE DIFFERENT CLAY MINERALS: FTIR SPECTROSCOPIC STUDY

The adsorption of an anionic surfactant LABS (Linear alkyl benzene-sulphonate) and a cationic surfactant DDAC (Distearly dimethyl ammonium chloride) by kaolinite, bentonite and sepiolite clays was investigated by vibrational spectroscopy. The samples prepared at different concentrations, and clay-surfactant spectra in the natural state, were recorded. The spectroscopic results indicate that the LABS and DDAC adsorbed on sepiolite and kaolinite. Bentonites are coordinated to either surface hydroxyls by H-bonding interacti on (sepiolite) or to exchangeable catoins (kaolinite, bentonite) through both sulphur and nitrogen atoms as ligands. Interactions of both surfactants showed similarities, in that LABS was coordinated on clay surfaces with broken ends, and the DDAC molecule was adsorbed on the clay surface.

Optimized geometry, vibration (IR and Raman) spectra and nonlinear optical activity of p-nitroanilinium perchlorate molecule: A theoretical study

Abstract The molecular modeling of p-nitroanilinium perchlorate molecule was carried out by using B3LYP and HSEH1PBE levels of density functional theory (DFT). The IR and Raman spectra were simulated and the assignments of vibrational modes were performed on the basis of relative contribution of various internal co-ordinates. NBO analysis was performed to demonstrate charge transfer, conjugative interactions and the formation of intramolecular hydrogen bonding interactions within PNAPC. Obtained large dipole moment values showed that PNAPC is a highly polarizable complex, and the charge transfer occurs within PNAPC. Hydrogen bonding and charge transfer interactions were also displayed by small HOMO-LUMO gap and molecular electrostatic potential (MEP) surface. The strong evidences that the material can be used as an efficient nonlinear optical (NLO) material of PNAPC were demonstrated by considerable polarizability and hyperpolarizability values obtained at DFT levels.

Molecular Structure, Vibrational Spectra and Chemical Shift Properties of C12H9ClO4 and C12H9BrO4 Crystals by Density Functional Theory and ab initio Hartree-Fock Calculations

The molecular geometry, vibrational spectra, and gauge including atomic orbital (GIAO), individual gauges for atoms in molecules (IGAIM), and continuous set of gauge transformations (CSGT) 1H and 13C chemical shift values of ethyl 6-chloro-2-oxo-2H-chromene-3-carboxylate (C12H9ClO4-(I)) and ethyl 6-bromo-2-oxo-2H-chromene-3-carboxylate (C12H9BrO4-(II)) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6- 31G+(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies were used to determine the types of molecular motions associated with the spectra of the experimental bands observed. Also, calculated 1H and 13C chemical shift values were compared with the experimental ones.

Dielectrical Properties of a Novel Porcelain Produced from Natural Clay, Waste Glass and Fly Ash

A novel porcelain was obtained by sintering 50% kaolinite clay, 25% waste glass and 25% fly ash (a byproduct of Turkey thermal power plant) at different temperatures of 1373-1523 Κ (ΠΟΟ-1250 °C). The microstructure and phase changes on heating were studied using SliM and XRD techniques. Fly ash used in this study contributed towards development of anorthite (CaO.Al2O3.2SiO2) phase by crystallization of melted glassy phase. In samples exposed to sintering for 5 hours in 1523 K, viscosity and porosity in the structure decreased when the glassy phase melted. Dielectric permittivity (real and imaginary), conductivity and tan8 as a function of temperature were analyzed at 10 KHz frequency. Samples exposed to sintering for 5 hours exhibit increased conductivity in the 200-260 °C temperature range. This observation corresponds to the settlement of changeable cations in more stable octahedral sites during sintering. These results are significant in terms of usability of waste materials like waste glass and fly ash in obtaining new generation materials and in electric-electronic industry.