Defect-Chemical Interpretation

According to the chemical diffusion theory of Wagner [28], the chemical diffusion coefficient of component oxygen is given as  

The thermodynamic factor can also be calculated from the defect structure. The oxygen nonstoichiometry is in general given as in Eq. (45) or Eq. (49). Differentiation leads to the thermodynamic factor as 

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Although it is possible to obtain good estimates of the electron correlation energy by either density functional or configuration interaction methods both of these methods (for different reasons) suffer from the same defect it is not possible to obtain a clear physical and chemical interpretation of the results of the calculation. The valence bond model, in principle and in practice, puts the physical interpretation as a top priority but pays a price in the complexity of its implementation. 

In defect-chemical equations the concentrations of electrons and electron holes are often written in terms of the law of mass action without specifying where the electronic defects are located. The concentrations of electronic defects are often interpreted in terms of the band theory of solids and in the following is... 

They form a monolayer that is rich in defects, but no second monolayer is observed. The interpretation of these results is not straightforward from a chemical point of view both the electrodeposition of low-valent Ge Iy species and the formation of Au-Ge or even Au Ge h compounds are possible. A similar result is obtained if the electrodeposition is performed from GeGl4. There, 250 20 pm high islands are also observed on the electrode surface. They can be oxidized reversibly and disappear completely from the surface. With Gel4 the oxidation is more complicated, because the electrode potential for the gold step oxidation is too close to that of the island electrodissolution, so that the two processes can hardly be distinguished. The gold step oxidation already occurs at -i-lO mV vs. the former open circuit potential, at h-485 mV the oxidation of iodide to iodine starts. 

Without any proof it has often been assumed that C equals C so that an estimate of rcl could be obtained which could be compared with the number of chemically crosslinked units, vc. Any differences were subsequently interpreted in terms of various network defects, as e.g. entanglements, closed loops, or unreacted functionalities. 

Ab initio quantum-chemical calculations were used in this study for the interpretation of the experimental data (EPR, IR, and optical). The main purpose of the calculations was to elucidate the question of how the geometric factors (spatial structure of the defect) and chemical ones (nature of the substituents) influence the spectral properties of the defects. At present time such calculations can be carried out on acceptable level for systems comparatively small in size. This makes it necessary to use molecular models for calculations of defects in solids. 

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