Meryem Evecen

Quantum chemical studies on the molecular structure, spectroscopic and electronic properties of (6-Methoxy-2-oxo-2H-chromen-4-yl)-methyl pyrrolidine-1-carbodithioate

Abstract In this paper, the molecular geometry, vibrational frequencies and chemical shifts of (6-Methoxy-2-oxo-2H-chromen-4-yl)methyl pyrrolidine-1-carbodithioate in the ground state have been calculated using the Hartree-Fock and density functional methods with the 6-311++G(d,p) basis set. To investigate the nonlinear optical properties of the title compound, the polarizability and the first hyperpolarizability were calculated. The conformational properties of the molecule have been determined by analyzing molecular energy properties. Using the time dependent density functional theory, electronic absorption spectra have been calculated. Frontier molecular orbitals, natural bond orbitals, natural atomic charges and thermodynamical parameters were also investigated by using the density functional theory calculations.

Molecular structure, spectroscopic, and density functional theory studies of o-Dianisidine

ABSTRACT o-Dianisidine has been characterized by the FT-IR, UV-Vis, and X-ray single-crystal determination. The compound crystallizes in the orthorhombic space group Pbca with a = 7.2593 (4) Å, b = 21.3485 (10) Å, c = 16.5835 (11) Å and Z = 8. Density functional theory has been used in the computation of the molecular geometry and harmonic vibrational wavenumbers. The calculated molecular geometry parameters have been compared with X-ray data. UV-Vis spectra of the compound have been predicted using the time-dependent density functional theory and good agreement between the calculated and experiment is determined. Besides, molecular electrostatic potential, frontier orbital analysis, and nonlinear optical properties were performed by using density functional theory calculations.

First principle study of structural, electronic, mechanical, dynamic and optical properties of half-Heusler compound LiScSi under pressure

ABSTRACT In this study, several physical properties of LiScSi compound with MgAgAs phase were investigated via the plane-wave pseudo-potential technique in density functional theory (DFT). The calculated total energy-atomic volume was fitted to the Murnaghan equation of state in order to obtain bulk modulus, their first derivatives and the lattice constant. These results were compared to findings of recent literature. Afterwards, the partial density of states (PDOS) and charge density differences were used to evaluate the electronic band structure of LiScSi under pressure. By analysing elastic properties (shear modulus, Poisson ratio, Young’s modulus, etc.) of the material, it has been shown that MgAgAs phase of the compound is mechanically stable under pressure. Moreover, the dynamical stability of this compound is calculated by means of the phonon dispersion curves and one-phonon DOS. Finally, the optical properties and related parameters (refractive index, dielectric function, and loss function) of LiScSi were examined with subject to different pressures.

Theoretical investigations on the structural, spectroscopic, electronic and thermodynamic properties of (3-Oxo-3H-benzo[f]chromen-1yl) methyl N,N-dimethylcarbamodithioate-1ex

Abstract Hartree-Fock and Density Functional Theory (B3LYP, B3PW91) calculations for the ground state of (3-Oxo-3Hbenzo[ f]chromen-1-yl) methyl N,N-dimethylcarbamodithioate have been presented and the calculated structural parameters and energetic properties have been compared with the available X-ray diffraction data. The vibrational frequencies have been calculated using optimized geometry of the molecule. The conformational properties of the molecule have been determined by computing molecular energy properties, in which torsional angle varied from -180° to +180° in steps of 10°. Moreover, natural bond orbital analysis and atomic charge analysis have been performed. Besides, HOMO and LUMO energies have been calculated and their pictures have been presented. Finally, molecular electrostatic potential and thermodynamic properties have been calculated. It is seen that the obtained theoretical results agree well with the available experimental values. In all the calculations, except for optimization and vibrational calculations, B3LYP level of theory with 6-311++G(d,p) basis set has been used.