Density functional theory atomic calculations

While in previous ab initio smdies the reconstructed surface was mostly simulated as Au(lll), Feng et al. [2005] have recently performed periodic density functional theory (DFT) calculations on a realistic system in which they used a (5 x 1) unit cell and added an additional atom to the first surface layer. In their calculations, the electrode potential was included by charging the slab and placing a reference electrode (with the counter charge) in the middle of the vacuum region. From the surface free energy curves, which were evaluated on the basis of experimentally measured capacities, they concluded that there is no necessity for specific ion adsorption [Bohnen and Kolb, 1998] and that the positive surface charge alone would be sufficient to lift the reconstmction. 

Recent density functional theory (DFT) calculations have been used to calculate the transfer of unpaired electron spin densities to the nearby atoms and analyze the orbitals involved in these mechanisms. For example. Figure 8 shows the spin densities obtained for Cr +-doped LiCo02. The spin densities can be calculated by subtracting the spin-up elec-... 

Shutov et al. carried out density functional theory (DFT) calculations on E[N(SiMe3)CH2CH2]3N (E = P, Sb, Bi) up to the PBE level of theory <2002IC6147>. The structural data obtained from geometry optimization on antimony and bismuth derivatives reproduced experimental trends, that is, a decrease in the Ndat-E distance from Sb to Bi. The values of electron density in Ndat-E critical point and the Laplacian of charge density for the azabismatrane indicated that a closed-shell interaction existed between Bi atom and Ndat atom. 

Computational studies suggest that the mechanism of the proline catalyzed aldol cyclization is best described by the nucleophilic addition of the neutral enamine to the carbonyl group together with hydrogen transfer from the proline carboxylic acid moiety to the developing alkoxide. A metal-free partial Zimmerman-Traxler-type transition state involving a chair-like arrangement of enamine and carbonyl atoms and the participation of only one proline molecule has been established [118,119]. On the basis of density functional theory (DFT) calculations Cordova and co-workers [120,121] have studied the primary amino acid intermolecular aldol reaction mechanism. They demonstrated that only one amino acid molecule is involved in the... 

Once the model is verified, e.g., through agreement between computed and experimental spectra, then it is possible to extract additional information on the bonding and interactions from the calculations that is not present in the experimental data [3], The experiment and typically Density Functional Theory (DFT) calculations go hand in hand and provide a full view of the electronic stracture and bond formation. Furthermore, XES provides a very strong basis for the evaluation of different theoretical methods for population analysis. Many different schemes subdividing the charge density into contributions assigned to specific atoms have been proposed, but the lack of means to directly measure the atomic populations in different orbitals has made aU methods somewhat arbitrary. The localized character of... 

Our previous work has shown that spin-coated films of zinc phthalocyanines exhibited detectable shifts in the optical absorption spectra during alcohol vapor exposure [5], We here report an investigation of the molecular interactions between zinc phthalocyanines and alcohols by the x-ray absorption spectroscopy, the phase contrast optical microscopy and the transmission electron microscopy. The experimental results are also compared with our Density Functional Theory (DFT) calculations of the interactions between alcohol molecules and the zinc atom of the phthalocyanines [5],... 

The important properties of the metal ammines when used as materials for indirect hydrogen storage can be understood and explained at the atomic scale. In this section, an atomic scale model of the sample system Mg(NH3)6Cl2 based on density functional theory (DFT) calculations shows how atomic structures, energies and dynamics can be connected to macro-scale properties such as shape, uptake and decomposition rates, porosity and reaction enthalpies. The model is based on experimentally observed structures (Olovsson, 1965 Partin and O Keeffe, 1991 Leineweber et al, 1999, 2000 Hummelshpj et al, 2006) and it is expected to be applicable to other metal ammines. A detailed understanding of the systems at the atomic scale is a prerequisite for the design of new and better materials. 

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