we have performed density functional theory (dft) calculations to investigate the properties of defect in arepresentative armchair model of silicon nanotubes (sints). to this aim, the structures of pristine and defective(5,5) sints have been optimized and the properties such as bond lengths, total energies, binding energies,.formation energies, gap energies, and dipole moments have been evaluat...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii 1 The Beginning of Molecular Electronics . . . . . . . . . . . . . . . . . . . . . 1 2 Modern Density Functional Theory . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 Quantum Many-body Theory . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 The Born-Oppenheimer Approximation . . . . . . . . . . . ....

Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to ...

The equations for the response terms for the fragment molecular orbital (FMO) method interfaced with the density functional theory (DFT) gradient are derived and implemented. Compared to the previous FMO-DFT gradient, which lacks response terms, the FMO-DFT analytic gradient has improved accuracy for a variety of functionals, when compared to numerical gradients. The FMO-DFT gradient agrees wit...

In this paper, the synthesis of various enaminones from the reaction of 3-aminocoumarin and ethyl-2,4-dioxo-4-arylbutanoate in the presence of p-toluene sulfonic acid is reported. The reaction was examined under different solvents and catalytic systems, which clearly proved the importance of acidic catalyst in this organic transformation. This work was also accompanied by density functional the...

We have performed density functional theory (DFT) calculations to investigate the properties of defect in arepresentative armchair model of silicon nanotubes (SiNTs). To this aim, the structures of pristine and defective(5,5) SiNTs have been optimized and the properties such as bond lengths, total energies, binding energies,.formation energies, gap energies, and dipole moments have been evaluat...

Here, new N,N′-dipyridoxyl(4,4''-diaminodiphenylether) Schiff-base ligand has been synthesized and characterized by IR, 1H NMR and mass spectrometry. Also, geometry optimization and theoretical assignment of IR spectrum of the ligand have been computed by employing density functional theory (DFT) method. Two pyridine rings and benzene rings in the bridge region are not in the same plane. The ca...

Density Functional Theory (DFT) calculations were employed to investigate the structural characteristics, electronic properties, and nonlinear optical properties of Benzyne-Based Chromophores at B3LYP/6-31G(d,p) level. The effects on the hyperpolarizabilities of various donor and acceptor substituent (H, F, Cl, Br, Me, NH2, OH, NH3+, COOH, CHO, CN, NO,NO2 ) were studied. The results reveale...

The Density Functional Theory (DFT) and the Natural Bond Orbital (NBO) calculations basedmethod B3LYP/6-31G* were carried out to study the interaction of carbon nanotube (8,0) withnitrobenzene in two situations perpendicular and parallel. Formation energies of compounds,charges, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular'orbital (LUMO) and the HOMO-LUMO ba...