Chemical local electronic structure propertie

The use of local electronic-structure properties conception in the chemical-bonding analysis was demonstrated also in ab-initio calculations of crystaUine metal oxides, discussed in the next section using the example of titanium oxides. 

Due to the covalent nature of chemical bonding, properties of zeolitic protons depend on local electronic structure details. This is illustrated in Fig. 10 [105]. Using a basis set that predicts the NMR quadrupole coupling constants (QCC), accurately measured QCCs in zeolite ZMS-5 for Al tetrahedra in the proton form and deprotonated Al tetrahedra (e.g., by cation exchange) are compared with predicted QCCs from cluster model calculations. One... 

Porous anodic alumina is a very promising material for nanoelectronics. The injection of different types of impurities inside an alumina matrix can substantially improve its electrophysical properties. It is very important to study the local environment (chemical bonds, electronic structure, etc.) of injected atoms for understanding physical principles of the electronic elements formation. A number of techniques can be used to determine a chemical state of atoms in near surface layers. The most informative and precise technique is X-ray photoelectron spectroscopy. At the same time, Auger electron spectroscopy (AES) is also used for a chemical analysis [1] and can be even applicable for an analysis of dielectrics. The chemical state analysis of Ti and Cu atoms implanted into anodic aliunina films was carried out in this work by means of AES. 

The nature of the triple bond, whether —C=C—, —C=N or ==N=N and their higher row analogues, has been reviewed several times in this series, in theoretical chapters. The nature of a chemical entity is defined by its geometric and electronic structural properties. The triple bond is characterized by short bond distances, local cylindrical symmetry, relatively high electron density prependicular to the bond axis and relatively large polarizability parallel to the bond axis. Its description in terms of a and n bonding is classic, and qualitatively explains the characteristic properties of the triple bond. 

Chemical Properties. Simple molecular-orbital theory predicts that many organometallic molecules should show electronic effects similar to conjugated systems, since the electronic structure is generally expressed in terms of molecular orbitals which involve both ring and metal orbitals. The ESR spectra (Sec. III.C) provide physical evidence for this formulation however correlation between chemical reactivities and theoretical quantities, such as charge densities and localization energies, which has been of use in aromatic systems (60) has not been attempted. Indeed, very few detailed kinetic studies of organometallic compounds have been reported with which to compare theory. We consider the different classes of compounds in turn. 

A physical approach to the electronic structure problems of solids contrasts sharply with the notion that local interactions dominate the structure and properties of molecular systems. Hence, it is very appealing to replace the infinite solid, which is difficult to treat quantum-chemically, by finite sites that can model considered species. Intuitively, cutouts from the bulk or the surface are made and treated like molecules. This type of method is called the cluster approach, and the models made as cutouts of the periodic structure are called cluster models [22]. 

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