Double phenomenology

The reader already familiar with some aspects of electrochemical promotion may want to jump directly to Chapters 4 and 5 which are the heart of this book. Chapter 4 epitomizes the phenomenology of NEMCA, Chapter 5 discusses its origin on the basis of a plethora of surface science and electrochemical techniques including ab initio quantum mechanical calculations. In Chapter 6 rigorous rules and a rigorous model are introduced for the first time both for electrochemical and for classical promotion. The kinetic model, which provides an excellent qualitative fit to the promotional rules and to the electrochemical and classical promotion data, is based on a simple concept Electrochemical and classical promotion is catalysis in presence of a controllable double layer. 

Due to linear dependence on the electron-nucleus mass ratio, the double logarithm contribution in (5.10) is nowadays very important for phenomenological analysis of the hydrogen-deuterium isotope shift (see Subsect. 12.1.7). 

The electrostatic aspects of electrochemical systems will be introduced first and the electrochemical potential as a key concept is presented (Sects. 1.2-1.4). The electrochemical equilibrium is discussed and Nemst s equation and standard and formal electrode potentials are introduced (Sect. 1.5). The study of electrochemical interfaces under equilibrium ends with the phenomenological and theoretical treatment of the electrical double layer (Sect. 1.6). 

Developing approach has given an explanation at what conditions the matrices with macroscopic non-uniformities (e.g., lamellar systems, heterogeneous inclusion phases, etc.) and with effective macroscopic diffusion coefficients in the latter case, a matrix is considered as a homogeneous one and when the phenomenological model of double sorption, which operates with sorption sites of two types could be used [190-192]. 

At a simple phenomenological level, the hydration force can be described via an exponentially decreasing force, additive to (and independent of) the DLVO double layer and van der Waals forces [10]. An alternative phenomenological description is to consider the existence of an order parameter" and a Landau-like expansion of the free energy in that parameter. When only some of the expansion terms are retained in the latter expansion, both phenomenological descriptions lead to similar behaviors for the hydration forces [11]. 

Ia) is included in the electronic Hamiltonian since, as we shall see, its most important effects arise from interactions involving electronic motions. The interactions which arise from electron spin, 30(5 ), will be derived later from relativistic quantum mechanics for the moment electron spin is introduced in a purely phenomenological manner. The electron-electron and electron-nuclear potential energies are included in equation (2.36) and the purely nuclear electrostatic repulsion is in equation (2.37). The double prime superscripts have been dropped for the sake of simplicity. We remind ourselves that // in equation (2.37) is the reduced nuclear mass, M M2/(M + M2). 

We now turn to the potential dependence of electrosorption of neutral molecules, considering first the model developed by Frumkin. This is a phenomenological model, which depends on considerations of the changes in the electrostatic energy of the interphase caused by adsorption. Assuming that measurements are taken in concentrated solutions of a supporting electrolyte, we can neglect diffuse-double-layer effects and focus our attention on the Helmholtz part of the double layer, considered as a parallel-plate capacitor. In the pure solvent the... 

In general, the phenomenological definition of specific adsorption depends on the model of the diffuse part of the double layer. However, at the potential of zero charge, the contribution of the nonspecific adsorption in the diffuse part of the double layer should be absent. According to the phenomenological definition of specific adsorption [53], at the point of zero charge it is said that there is specific adsorption if the measured surface excess of any ionic species is positive. 

Although, of course, Ge atoms are immobile, electrons can move in from a neighbouring Ge atom to the effect that the Ge atom moves the other way. Phenomenologically speaking, holes are mobile. Their mobilities should not be underestimated in Ge crystals at room temperature, they are about half as high as those for electrons. The upshot is that in electronic semiconductors, electrons and holes assume the functions that anions and cations have in electrolytes and, consequently, in establishing the space charge density in the double layer. 

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