Relative dielectric constant

Tafel slope (Napieran loop) transfer coefficient diffusion layer thickness dielectric constant, relative electric field constant = 8.85 x 10 F cm overvoltage, polarization ohmic voltage drop, resistance polarization specific conductance, conductivity electrochemical potential of material X,... 

Dielectric Constant (Relative Permittivity) Sr (dimensionless) (dimensionless)... 

Physical properties of the solvent are used to describe polarity scales. These include both bulk properties, such as dielectric constant (relative permittivity), refractive index, latent heat of fusion, and vaporization, and molecular properties, such as dipole moment. A second set of polarity assessments has used measures of the chemical interactions between solvents and convenient reference solutes (see table 3.2). Polarity is a subjective phenomenon. (To a synthetic organic chemist, dichloromethane may be a polar solvent, whereas to an inorganic chemist, who is used to water, liquid ammonia, and concentrated sulfuric acid, dichloromethane has low polarity.)... 

A further problem is that ion association, that is, the tendency of oppositely charged ions to form pairs or larger aggregates in solution, becomes increasingly important as the temperature rises unless the density is kept constant this is because ion association is inversely related to the dielectric constant (relative permittivity) of the medium, which is correlated with density for a given solvent. Helgeson and co-workers have attacked these problems theoretically for aqueous solutions up to 1000 °C.28 For our purposes, it is enough to note that quantitative treatment of ionic reactions in sub- and supercritical aqueous solutions is extremely difficult at present, and likely to remain so for some time. 

Table 1.4 Dielectric constants (relative permittivities) at 20°C for some common solvents...

We will summarize the two electrical properties which define the electrical characteristics, namely, the dielectric constant relative to free space e and the conductivity a. Both properties change with temperature and strongly with frequency. As a matter of fact, as the frequency increases from a few Hertz to gigahertz, the dielectric constant decreases from several million to only a few units. Concurrently, the conductivity increases from a few mMho/cm to nearly a thousand. 

Hafnium oxynitride (Hf-O-N) thin films have attracted interest because of their unique properties, particularly their high dielectric constant, relatively large... 

Clausius-Mossotti equation — Named after Clausius and Ottaviano Fabrizio Mossotti (1791-1863). It relates the electron -> polarizability a of an individual molecule to the optical -> dielectric constant (relative permittivity) r of the bulk material. 

Cyclotrimerization of polyfunctional aryl acetylenes offers a unique route to a class of highly aromatic polymers of potential value to the micro-electronics industry. These polymers have high thermal stability and improved melt planarization as well as decreased water absorption and dielectric constant, relative to polyimides. Copolymerization of two or more monomers is often necessary to achieve the proper combination of polymer properties. Use of this type of condensation polymerization reaction with monomers of different reactivity can lead to a heterogeneous polymer. Accordingly, the relative rates of cyclotrimerization of six para-substituted aryl acetylenes were determined. These relative rates were found to closely follow both the Hammett values and the spectroscopic constants A h and AfiCp for the para substituents. With this information, production of such heterogeneous materials can be either avoided or controlled. 

The Poisson Equation From classical electrostatics, the free charge density p(r)—that is, the charge density due to the solute as opposed to the polarization charges in the solvent—in a continuous medium of homogeneous dielectric constant (relative permittivity) e, where r denotes the position in space, is related to the electrostatic potential, ( )(r), by Poisson s equation, which takes the following form, in this case in Gaussian units ... 

If all of the atoms and charges in the system of interest are explicitly represented and atomic polarization is included, the use of a dielectric constant other than unity would be inappropriate. A variety of models has been used, however, to approximate the dielectric behavior of a macromolecular system where the solvent was not explicitly included. Dielectric constants for the protein interior between 2 and 10 have been employed, as has a distance-dependent dielectric response equal to the distance in angstroms.78 Also, simple forms of the Kirkwood-Westheimer-Tanford model79 have been used to approximate the effect of the aqueous solvent. An approach that may improve our understanding in this area employs linear response theory to evaluate the spatially dependent dielectric response.80 In any such model it is necessary to consider the frequency dependence of the dielectric constant relative to the time scale of the dynamic process under consideration. 

The dielectric constant (relative permittivity) is a macroscopic property. If molecules 1 and 2 approach each other so closely, there will be no room for a solvent molecule between them. Then we may question the use of the medium s r in the denominator of the related expressions, because if any polarization takes place, this may be due to a much smaller effective value of r. On the other hand, some associated solvents apply forces on solute molecules, which are determined mainly by the orientation of the molecules of 1 and 2 in the medium 3, so that the resultant distribution functions are not only functions of r but also dependent on the orientation angle. 

Together with the definition of the dielectric constant (relative permittivity), e = 1+ 4ny, this leads to ... 

This table gives properties of compressed water and superheated steam at selected pressures and temperatures. The properties included are density p, enthalpy//, entropy S, heat capacity at constant pressure C, and static dielectric constant (relative permittivity). The table was generated from the formulation approved by the International Association for the Properties of Water and Steam for general and scientific use. The reference state for this table is the liquid at the triple point, at which the internal energy and entropy are taken as zero. A duplicate entry in the temperature column indicates a phase transition (liquid-vapor) at that temperature property values are then given for both phases. In the 100 MPa section of the table, an entry is given at the critical temperature, 647.10 K. Temperatures refer to the ITS-90 scale, on which the normal boiling point of water is 373.12 K (99.97°C). 

Empirical ionic radius correction in the modified Born Eq. (4) equal to 0.080 nm for cations and 0.017 nm for anions Dielectric constant (relative permittivity) of the bulk solvent subscripts S and W refer respectively to solvent and water... 

---