Electronic properties geometric structures

This allows a direct influence of the alloying component on the electronic properties of these unique Pt near-surface formations from subsurface layers, which is the crucial difference in these materials. In addition, the electronic and geometric structures of skin and skeleton were found to be different for example, the skin surface is smoother and the band center position with respect to the metallic Fermi level is downshifted for skin surfaces (Fig. 8.12) [Stamenkovic et al., 2006a] owing to the higher content of non-Pt atoms in the second layer. On both types of surface, the relationship between the specific activity for the oxygen reduction reaction (ORR) and the tf-band center position exhibits a volcano-shape, with the maximum... 

The unique properties of the proton have been attributed by some authors to the fact that it has no electronic or geometric structure. The absence of any electron shell implies that it will have a radius that is about 105 times smaller than any other cation and that there will be no repulsive interactions between electron clouds as a proton approaches another reactant species. The lack of any geometric or electronic structure also implies that there will not be any steric limitations with regard to orientation of the proton. However, it still must attack the other reactant molecule at the appropriate site. 

NMR and EPR techniques provide unique information on the microscopic properties of solids, such as symmetry of atomic sites, covalent character of bonds, strength of exchange interactions, and rates of atomic and molecular motion. The recent developments of nuclear double resonance, the Overhauser effect, and ENDOR will allow further elucidation of these properties. Since the catalytic characteristics of solids are presumably related to the detailed electronic and geometric structure of solids, a correlation between the results of magnetic resonance studies and cata lytic properties can occur. The limitation of NMR lies in the fact that only certain nuclei are suitable for study in polycrystalline or amorphous solids while EPR is limited in that only paramagnetic species may be observed. These limitations, however, are counter-balanced by the wealth of information that can be obtained when the techniques are applicable. 

In the present article we will not try to give an exhaustive compilation of nickel(III) and nickel(IV) complexes due to the large amount of work which is currently being undertaken in the field. Particular attention will be placed on those complexes whose properties have been investigated with the largest number of experimental techniques to have a better description of the electronic and geometrical structure of the compounds. 

The underlying motivation of the work presented in this paper is to provide a theoretical understanding of basic physical and chemical properties and processes of relevance in photoelectrochemical devices based on nanostructured transition metal oxides. In this context, fundamental problems concerning the binding of adsorbed molecules to complex surfaces, electron transfer between adsorbate and solid, effects of intercalated ions and defects on electronic and geometric structure, etc., must be addressed, as well as methodological aspects, such as efficiency and reliability of different computational schemes, cluster models versus periodic ones, etc.. 

Chirality is an important topic in chemistry and biochemistry, due to the natural occurrence of chiral molecules in living organisms. In circular dichroism (CD) one measures the differential absorption of left- and right-handed circularly polarized light, which for chiral species are different. Therefore, CD has turned out to be a powerful tool which provides information on the electronic and geometric structure of chiral molecules. Since most CD spectra are measured in solution we extended our DRF/TDDFT method to also calculate such properties. As a first example we studied... 

The benzene and azabenzenes form iso-electronic series of molecules, as naphthalene and the azanaphthalenes also do. The ground state electronic and geometric structures are therefore quite similar within one series. The substitution of CH groups with nitrogens introduces lone-pair to 7r transitions, and lowers the benzene and naphthalene symmetries. Small and systematic trends are found for linear response properties of the azabenzenes [189]. Each molecule is, however, very specific with respect to phosphorescence due to the delicate nature of the SOC and electric dipole activity interactions. 

A 7i-conjugated systems is a molecule along the backbone of which occurs a continuous path of carbon atoms or heteroatoms, each carrying a p atomic orbital. The determination of the electronic structure of conjugated systems and their properties in terms of energy, electron and hole transport is very difficult. Electron correlation effects must be taken into account and the strong connection between, and mutual influence of, the electronic and geometric structures should be evaluated [91]. 

In this chapter, we describe the size-dependent physical eind chemical properties of metal clusters and ions isolated in the gas phase and supported on solid surfaces from experimental points of view. At first, the methodologies and procedures employed in the experimental studies are surveyed for the readers who are not familiar with this field. Then we refer to size-specific features of the electronic and geometric structures of isolated metal-cluster ions together with their magnetic properties. 

Structural, physical and chemical properties of bulk rare earth oxides can be found in Chapter 27, Volume 3 of this series and have been compiled with a view towards catalysis in a recent review by Rosynek (1977). An important parameter for the catalytic behavior of rare earth oxides is their basicity. The basicities of rare earth oxides resemble those of the alkaline-earth oxides, and scale directly with the respective cation radii. Thus, La203 shows the strongest basicity and SC2O3 the weakest, with sesquioxide basicities decreasing smoothly along the lanthanide series going from La to Lu. This periodic trend allows one to study the influence of subtle variations in basicity on catalytic behavior in a class of related materials with similar electronic and geometrical structure. 

The X-ray absorption spectroscopy (XAS) methods provide information about the electronic and structural properties of matter. Thus, X-ray absorption nearedge spectroscopy (XANES) is adequate for the observation of local electronic and geometric structures of elements, while extended X-ray absorption fine structure (EXAFS) provides information concerning the coordination environment of metals, metal ions, and nonmetals. To improve time resolution and spectral quahty, sophisticated techniques such as EDXAFS (energy-dispersive X-ray absorption fine structure spectroscopy) and HERFD XAS (high-energy resolution fluorescence detection X-ray absorption spectroscopy) have been developed. All mentioned X-ray methods have a common requirement for high-briUiance X-ray sources such as available at a synchrotron. 

The crucial elementary steps in heterogeneous catalysis such as adsorption, dissociation and interaction of reactant molecules, and formation and desorption of products take place at the solid surface of the catalyst. These steps are sensitively influenced hy the composition, the electronic and geometrical structure of the surface, which may differ markedly from the bulk properties. The vital role of such surface processes in heterogeneous oxidation catalysis was one of the driving forces in the development of surface analytical techniques. 

Excimer formation is only to be expected when the concentration of the complex is high, and its excited state lifetime is long. Both excimers and exciplexes are new electronically excited species that have their own individual electronic and geometrical structures, vibrational energy levels, and excited state reactivities. Both excimers and exciplexes are also expected to have their own characteristic fluorescent and phosphorescent properties, which will be different from those of the... 

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