Oxide geometric structure

Dinitrogen oxide is a colourless gas the molecule has the geometric structure N—N—O, and is a resonance hybrid of the two forms... 

Sherer et al.32 carried out systematic DFT calculations (DFT = density functional calculations) on the compound in question and on pertinent simpler compounds. They optimized the geometric structures and compared the computed bond lengths and bond orders. These authors, too, chose the oxidation state II for the central palladium atom. 

The chemistry of metal oxides can be understood only when their crystal structure is understood. Knowledge of the geometric structure is thus a prerequisite to understanding the properties of metal oxides. The bulk structure of polycrystalline solids can usually be determined by x-ray... 

Molecular orbital calculations have been performed on compounds 19 and 20 . The calculated PM3 equilibrium geometric structures show that these compounds are severely distorted from planarity in accordance with X-ray structural analysis (see Section 8.I2.3.I). On the other hand, PM3 calculations performed on both neutral and oxidized/reduced compounds show that oxidation and reduction induce a clear gain of aromaticity. Predictions using the nonempirical valence effective Hamiltonian (VEH) method have shown that the electronic charge density in the highest occupied molecular orbital (HOMO) is localized on the benzodithiin 19 or benzoxathiin 20 rings. 

As discussed in Section II, STM images generally represent a rather complicated convolution of both electronic and geometric structures on the surface. This is especially true for oxides or sulfides such as M0S2, which generally exhibit a band gap. In light of this fact, it cannot a priori be determined whether the hexagonally... 

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.. 

The term photochromism can be defined as a light-driven reversible transformation between two isomers possessing different absorption spectra.111,21 The two isomers differ from one another not only in their absorption spectra, but also in their geometrical structures, oxidation/reduction potentials, refractive indices, and dielectric constants. When such photochromic chromophores are incorporated into functional molecules, such as polymers, host molecules, conductive molecular wires, or liquid crystals, the functions can be switched by photoirradiation.[3 61 Photostimulated reversible changes in refractive index can also be applied to optical waveguide switching.171 This chapter reviews applications of photochromic chromophores, especially diar-ylethene derivatives, in various photo switching molecular systems. 

The geometric structural parameters of a number of A-oxides generated from 1,3-dithietane and keto and thioketo derivatives generated from 2,2,4,4-tetrafluoro-l,3-dithietane have been recently calculated at the Hartree-Fock (HF)/6-31-G level, within the molecular orbital (MO) theory framework <1999JMT(466)111>. Structures shown here show the optimized geometries of the parent 1,3-dithietane 1, its mono- and bis-oxides 2-4, l,l -dioxide 5, l,3,3 -trioxide 6, and l,l, 3,3 -tetraoxide 7, whereas Table 1 lists the selected bond distances and angles for these compounds. 

QEXAFS scans (30-90 seconds per scan) is suitable to study reactions like pretreatment processes. The whiteline area gives information concerning the oxidation state. The EXAFS region represents the geometrical structure of the Pt atom. The final metal particle size was obtained from the Pt-Pt first shell coordination number, H2 chemisorption26 as well as HRTEM. 

The geometric structure of the intetface. Many catalytic reactions are surface sensitive and it is well known that the metal-support interactions are strongly textural and stochiometrically dependent [11,14]. Moreover, it is of particular interest to understand if the metal clusters introduce new active sites, where chemical reactions can occur on the oxide support. 

Improvement of the geometric structures of the auxiliary phases using the PEVD technique will benefit the performance of gaseous oxide sensors in many ways, e.g., increasing selectivity and stability, shortening response time, and decreasing the influence of gas flow rate. °... 

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