Diffusivity various charge states

For diffusion models based on self-interstitials, C° Cv°. Dopant diffusion and self-diffusion are assumed to occur via an interstitialcy mechanism (32). Mobile complexes consisting of self-interstitials in various charge states and impurities are assumed to exist. 

The diffusivity of the dopant can be different through vacancies of various charge states. The total diffusivity of a dopant might be, for example [2]... 

In the following we will study in more detail chemical diffusion and in particular the situation with various charge carriers. Let us concentrate on the case that, besides electrons and holes, oxygen ions in different valence states are mobile via interstitial and/or vacancy defects. 

The initiation of an electrogenic process causes an adjustment of the passive ionic fluxes across the membrane. In particular, the net charge actively brought in is soon electrically compensated by appropriate passive movements of that ion and other ions into or out of the cell. The actual electrical potential difference across the membrane then results from the diffusion potential caused by these new passive fluxes plus a steady-state contribution from the electrogenic process involving the active transport of various charged species. We can represent the electrical potential difference generated by the active transport of species/, atj, by... 

FIGURE 2.7 Ratio of /l predicated by the dynamic EDL model in combination of the 3-state dielectric model over i i for the reduction of variously charged reactants at electrodes of different sizes. Other parameters are the same as that for Figure 2.3. (Reprinted with permission from He, R., Chen, S.L., Yang, F., and Wu, B.L., Dynamic diffuse double-layer model for the electrochemistry of nanometer-sized electrodes, J. Phys. Chem. B, 2006, 110, 3262-3270. Copyright 2006 American Chemical Society.)... 

As already stated in Section 3.3.2, the precise values of the potential of the diffuse electric layer (po can be obtained by the method of equilibrium foam film . The results correlate well with the values of the electrokinetic potential, measured by the method of the rotating bubble [65], Table 8.1 presents the -potential values and the surface charge density Oo for foams from various surfactant kinds [65]. 

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