The structure and surface energies of the cleaved, reconstructed, and fully hydroxylated (001) alpha-quartz surface of various thicknesses are investigated with periodic density functional theory (DFT). The properties of the cleaved and hydroxylated surface are reproduced with a slab thickness of 18 atomic layers, while a thicker 27-layer slab is necessary for the reconstructed surface. The per...

The structure and surface energies of the cleaved, reconstructed, and fully hydroxylated (001) a-quartz surface of various thicknesses are investigated with periodic density functional theory (DFT). The properties of the cleaved and hydroxylated surface are reproduced with a slab thickness of 18 atomic layers, while a thicker 27-layer slab is necessary for the reconstructed surface. The perform...

We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of...

The synthesis and characterization of different ether and ester derivatives of 8-hydroxyquinoline have been made. UV-visible and fluorescence spectra of these compounds have revealed spectral dependence on both solvent and O-substituent. The fluorescence intensity of ether derivatives revealed higher intensity for 8-octyloxyquinoline compared with 8-methoxyquinoline, whereas those of ester deri...

Theoretical studies have been carried out on bio active molecules such as Naphthalene (npa) and its derivatives naphthalene-2-sulfonic acid (nsa) 1-nitroso-2-naphthol (nnol) using both Ab initio HF DFT-B3LYP methods with 6-311++G(d,2p) basis sets. The geometrical parameters, molecular properties vibrational spectra of nsa, nnol npa were calculated analyzed. Geometrical optimizations the done by...

Most of the main features of water oxidation in photosystem II are now quite well understood, including the mechanism for O-O bond formation. For the intermediate S2 and S3 structures there is also nearly complete agreement between theory and experiments. Given the present high degree of consensus between theory and spectroscopic experiments for these structures, it is of high interest to go ba...

Using the long-range correction (LC) density functional theory (DFT) scheme introduced by Iikura et al. [J. Chem. Phys. 115, 3540 (2001)] and the Coulomb-attenuating model (CAM-B3LYP) of Yanai et al. [Chem. Phys. Lett. 393, 51 (2004)], we have calculated a series of properties that are known to be poorly reproduced by standard functionals: Bond length alternation of pi-conjugated polymers, pola...

Static excited-state polarisabilities and hyperpolarisabilities of three Ru(II) ammine complexes are computed at the density functional theory (DFT) and several correlated ab initio levels. Most accurate modelling of the low energy electronic absorption spectrum is obtained with the hybrid functionals B3LYP, B3P86 or M06 for the complex [Ru(II)(NH3)5(MeQ(+))](3+) (MeQ(+)=N-methyl-4,4'-bipyridin...

Studies of benzylidyne and its derivatives are of great interest due to their biological, pharmaceutical and industrial importance. In the present investigation, the vibrational wave numbers, geometrical parameters, modes of vibrations, minimum energy, NBO and 1H and 13C NMR chemical shifts of 3-Hydroxy benzylidyne Trifluoride (3HBT) are calculated with DFT/ B3LYP level of theory with 6-31+G(d)...