Kink site position separation from

RT In vwinif represent the enthalpic and entropic contributions, respectively. The separation work of an atom from a kink site position into a vacuum is equal to the sublimation enthalpy, AsubA, of the crystal assumed as infinitely large ... 

In the process of sublimation the atom is separated from a special position on the surface, the kink site position (half crystal position). In the ideal kink site position the... 

In this diagram the reaction of an ad-atom with the kink site position is reversible. But in the kink site position an atom may return to its previous position by separation from the kink site position, or it may become fixed in the crystal lattice by the next atom deposited in the kink site position. The built-in process is then completed. In this model, the kink site position has a similar function as the transition state in the theory of chemical reactions. 

Ad-atoms can be deposited into a kink site position either directly or via a step position. Otherwise, the atom in a kink site position can be separated from the kink site position to a step position or to an ad-atom position as shown in Figure 7.13. 

The separation from a kink site position is a reaction of first order. The reaction rate is given by the rate equation... 

What happens to an atom in the kink site position This may be determined by the time interval in which the atom stays in the kink site position. This time is called residence time in the kink site position (in German Verweilzeit )- The residence time is the statistical average of the time between the arrival of the atom in the kink site position and its separation from the kink site position. During the residence time the process of separation from the kink site position competes with the arrival of new atoms. The residence time t in a kink site position is given by the reciprocal value of the rate constant of separation. 

Comparison of the dynamic of some metals with cep and hep structures rate constants of separation from kink site positions (calculated with the assumption that the activation energy is proportional to the cleavage of one bond nd residence time t... 

The nature of the atom in the kink site position determines the reactivity of the kink site position in the next step, when a new atom is added to the kink site thus incorporating the atom in the kink site position into the lattice and forming a new type of kink site position, or the atom last included is separated from the kink site position (transition to the previous type). These reactions either lead to a reproduction of the existing kink site position, AB or BA or to new kink site positions, AA and BB. It depends on the stability of the new kink site positions whether the strong stoichiometry continues or whether new structures will be developed, either a eutectic mixture or a solid solution. 

Similar to metal deposition the overall reaction can consist of partial reactions such as the separation from the kink site position to an ad-atom position followed by the transfer to the electrolyte. This will be described in more detail in the next section. To compensate the electron release a reduction process is necessary. In an acid environment (an acid solution) protons can be reduced... 

As for deposition, the transition state of dissolution of a crystalline metal is the kink site position. From the kink site position there are two ways for separation (Figure 10.4). 

A) The transfer from the kink site position or step position, respectively to the ad-atom position (separation) followed by the transfer of the ad-atoms to the electrolyte (desorption). This can be described by the following two equations ... 

The first equation describes the reproduction of the kink site position in the process of separation of an atom from the kink site position and formation of an ad-atom. The second step represents desorption of the ad-atom. The charge transfer is split. Following the description of partial charge transfer in Section 4.3 with the introduction of a partial charge transfer coefficient A the charge transfer in the first step is = Xz, and the charge transfer in the second step Az j = (1 — A )z. The intermediate ad-atom can be a lower valent oxidation state stabilized as an anion complex. 

Cathodic activation energy, Galvani potential difference Aq> = 0 Activation energy of separation of atom A from kink site position AA Activation energy of separation of atom B from kink site position AB Activation energy of separation of atom A from kink site position BA Activation energy of separation of atom B from kink site position BB Free corrosion potential Diffusion potential Electron energy... 

Soliton (Fig. 2c) is a term used by physicists in various connections. From the chemist s point of view, a soliton is a positive, negative, or neutral radical-like site and corresponding conformational kink in the simple conjugated system of polyacetylene separating two semiinfinite conjugated chains. As with the polaron and bipolaron in other CPs, the soliton is mobile in the chain and is thought to be the charge carrier in poly acetylene. 

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