Analysis of the Electronic Structure

The previous analysis of the electronic structure of the carbon nanotubes assumed that we could neglect curvature effects, treating the nanotube as a single... 

Arai, T., J. Chem, Phys. 26, 435, New approach to the quantum-mechanical analysis of the electronic structure of molecules. The method of deformed atoms in molecules. A modification of Moffitt s method. 

Some typical reactions in the pseudoexcitation band are reviewed in this section. The importance of pseudoexcitation [1] in chemical reactions was supported by the detailed numerical analysis of the electronic structures of the transion states [66]. The concept of pseudoexcitation appeared in physics [67-69]. 

The relative intensities of the bands, i.e. the band-area ratios, are very meaningful for the interpretation of a PE spectrum since they are proportional to the relative probabilities of ionization. The absolute value of the area of a spectral band depends, among other factors to be discussed shortly, also on the density of the target, which is quite difficult to measure, so that usually the spectral intensities are given in arbitrary units. For the purpose of the analysis of the electronic structure of a molecule, the intensity ratio between the different bands is sufficient to give valuable indications. 

All chemical transformations relevant to metal/olefin reactions occur at the three orbitals in the plane between the two Cp rings or between the Cp and the N atom in the case of the CGC catalysts. This plane is usually referred to as the wedge or belt of the catalyst. The first detailed analysis of the electronic structure of group 4 metallocenes, and the implications on their chemistry, was performed by Lauher and Hoffmann with simple... 

Experimentally, derivatives 33b-d were synthesized and fully characterized [13]. These planar non-classical organoboranes exhibit a unique chemistry [13]. We first described 33b-d as valence-isomeric boriranylideneboranes 33 b d until their electronic structure was understood during the theoretical analysis of the electronic structure of 12a [44] (Scheme 3.2-17). The synthesis of derivatives of 34B, which is isoelectronic with 12B, remains a challenge. 

Authors [143] suppose that sulfur atoms are not affected by oxidation and only act as activating double bond substituents. However, the analysis of the electronic structure of tetrathiofulvalene shows that, resulting from the interaction of tt CC) and 7t(S) orbitals, HOMO of this molecule is an antibonding combination of jr and riji orbitals with the predominant contribution being from the latter. Indeed, the substitution of one or more S atoms with Se results in a less conjugated system and, as a consequence, in higher oxidation potentials [144]. 

Complexes 75 are remarkably stable at room temperature in the solid state and, when heated, they start to decompose only at about 130 °C (Cr) or 145 °C (W). Such a thermal stability is undoubtedly associated with their strongly dipolar nature, in which six possible ylide-type resonance forms contribute to the bonding (Fig. 12). As expected, analysis of the electronic structure of complex [W (=C=C=C=C=C=C=C(NMe2)2 (CO)5] by DPT methods showed that the LUMO is mostly localized on the odd carbon atoms of the chain, whereas the HOMO is on the even carbons. In accord with these electronic features, it was found that [W =C=C=C=C=C=C=C(NMe2)21(00)5] readily adds dimethylamine across the 05=05 bond, to give the isolable alkenyl-pentatetraenylidene derivative [W =C=C=C=C=C(NMe2)CH=C(NMe2)21(00)5] [69, 70]. 

Adsorption of saturated hydrocarbons on a Cu substrate provides a good model system for investigating the electronic structure since the rf-band interaction appears entirely in the occupied states, making the effects more clearly visible and the analysis of the electronic structure easier. There is an advantage to use the (110) surface with a two-fold symmetry if the molecule adsorbs with preferential alignment allowing projection of the electronic structure in three directions as discussed in the previous sections. 

Hypervalent carbocations have received some attention this year.14 The concept of three-centre, two-electron bonding in these entities is supported by a topological bifurcation analysis of the electronic structure of CH5 15 this and the related species CHg+ and CH3+ are also the subject of a review.16 The CHj + H2 reaction has been studied theoretically.17... 

In this section we have considered a family of semiempirical methods of analysis of the electronic structure of molecules, using the trial wave function in the form of the antisymmetrized product of strictly local geminals. The studies performed on these methods allow us to conclude that ... 

By contrast, quantum chemical methods allow, in principle, the analysis of the electronic structures of molecules with regard to chemical attacks at every site. Moreover, global reactivity parameters such as molecular electronegativity (see below) can be quantified. In addition, besides... 

D2, which has an acute bond angle of ca 90° (Figure 9). The analysis of the electronic structure of D1 and D2 showed that the HOMO of the former isomer is the Pb—Pb 7T-orbital, while the LUMO is a lead lone-pair type orbital. Strnctnre D2 has the frontier orbitals reversed, i.e. the lead lone-pair orbital is the HOMO and the Pb—Pb 7r-orbital is the LUMO. This is shown in Figure 10. It means that lead has a valence shell with an electron sextet. Nevertheless structure D2 is lower in energy than Dl. However, both structures Dl and D2 are not minima on the PES. The results were important, though, because the calculations showed that bulky substituents stabilize D2 so much that it not only becomes an energy minimum but even the global minimum on the PES. ... 

The earliest report we know of combining quantum chemistry with the atmosphere deals with the excitation of nitrogen and oxygen molecules as the primary event in the photo-excitation of the atmosphere. Krauss et al. reported theoretical calculations of the electronic properties of the molecules required for the prediction of optical emissions from normal and disturbed atmospheres, including the analysis of the electronic structure of excited states of nitrogen [2]. 

What is the physical origin of the transition-state valency relationship An analysis of the electronic structures of the initial, transition, and final states reveals that an answer to this question lies in the p orbitals of the adsorbates (except chemisorbed H). We find... 

The theoretical results obtained in the present work, strongly support the conclusions of Sheppard [46] and of Lehwald et al [67]. The results in Table 10 show that the molecule binds strongly on a Ni(lOO) surface, the geometry and the electronic structure of the molecule are highly perturbed by the adsorption process, and the di-CT adsorption mode is more stable than the 7t mode, by approximately 91 kJmoT. The calculated CC bond length for the di-a mode, 1.46 A, is identical to the experimental value determined by NEXAFS [68]. An analysis of the electronic structure shows that on both adsorption complexes the degree of the [Pg.236]

A more complete view of the electronic structure of Mg2Si04 may be obtained by comparing its photoelectron spectra with Si, Mg, and O x-ray emission spectra (Al-Kadier et al., 1984). The only feature not seen in our previous analysis of the electronic structure of Si02 is the position of the Mg 3p-0 2p bonding orbitals. From the data of Urch (1985) shown in Fig. 5.7, we see that the Mg p character, as shown in the Mg x-ray emission spectrum, occurs both in the predominantly O 2s orbital set and... 

Fleischauer has carried out a detailed analysis of the electronic structure of molybdenum disulphide. This analysis showed that all the accessible orbital electrons for both molybdenum and sulphur are used in intralaver bonding, leaving only high-energy antibonding orbitals available for bonding between layers or for basal surface adhesion to substrates. There are no accessible orbital electrons on either... 

This technique has been applied in the analysis of the electronic structure of stoichiometric and non-stoichiometric (111) surfaces of BaFj and CaF2 crystals [85-88] or in the case of AI2O3 crystals by Guo, Ellis and Lam [89-91]. Vg t could also represent an applied static electric field as used for evaluation of static polarizabilities as discussed below. In the latter case, we could evaluate the multipolar moments separately, thus obtaining the static polarizability, induced by a field of the form [92]... 

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