Electrostatic field Coulomb

The methodology of stochastic treatment of e-ion recombination kinetics is basically the same as for neutrals, except that the appropriate electrostatic field term must be included (see Sect. 7.3.1). This means the coulombic field in the dielectric for an isolated pair and, in the multiple ion-pair case, the field due to all unrecombined charges on each electron and ion. All the three methods of stochastic analysis—random flight Monte Carlo (MC), independent reaction time (IRT), and the master equation (ME)—have been used (Pimblott and Green, 1995). 

Theoretical aspects of the bond valence model have been discussed by Jansen and Block (1991), Jansen et al. (1992), Burdett and Hawthorne (1993), and Urusov (1995). Recently Preiser et al. (1999) have shown that the rules of the bond valence model can be derived theoretically using the same assumptions as those made for the ionic model. The Coulomb field of an ionic crystal naturally partitions itself into localized chemical bonds whose valence is equal to the flux linking the cation to the anion (Chapter 2). The bond valence model is thus an alternative representation of the ionic model, one based on the electrostatic field rather than energy. The two descriptions are thus equivalent and complementary but, as shown in Section 2.3 and discussed further in Section 14.1.1, both apply equally well to all types of acid-base bonds, covalent as well as ionic. 

The electron then would possess potential energy due to its position in the electrostatic field of the nucleus and kinetic energy by virtue of its motion. Its total energy would be the sum of these two energy terms. Designating the electrostatic potential by V, its value can be derived from Coulomb s Law... 

Please note that the electrostatic double-layer force is fundamentally different from the Coulomb force. For example, if we consider two identical spherical particles of radius R you cannot take Eq. (6.1), insert the total surface charge as Qi and Q2, use the dielectric permittivity of water and expect to get a reasonable result. The main differences are the free charges (ions) in solution. They screen the electrostatic field emanating from the surfaces. 

When an ion is adsorbed on the surface of a dielectric, itself consisting of ions, we may expect Coulomb forces to act between the ions of the adsorbent and the adsorbed ion. A positive ion, adsorbed on top of a negative ion of an adsorbent, is attracted by this ion, but it is repelled by the ions surrounding the one with which it is in direct contact, attracted again by the then following ions, etc. The result is a rather weak attraction. Hiickel (S3) derived the following equation for the electrostatic field emanating from a cubic face of the surface of an alkali halide crystal ... 

Although the interactions of charged, dipolar or polarizable groups have been investigated for various purposes, they have not often been utilized in the context of stereoselectivity. In fact, when coulombic effects were considered in the SN2 or E2 processes, their role was regarded as unimportant (Ingold, 1953 Cristol, et al., 1951). In view of the substantial electrostatic (field) effects estimated for polar substituents on the pA s of carboxylic acids (Tanford, 1958), metal-ion coordination (Basolo and Pearson, 1967), etc., it will be interesting to see what effects there may be on SS. 

It is easy to recognize in < >(r) the tensorial expression for the retarded field created at the point r by a dipole located at the origin r = 0. The instantaneous term in 1 jr3 coincides, in the approximation of the retarded effects, with the electrostatic field and reestablishes the coulombic dipole-dipole interaction. We shall investigate < >(r) at distances short compared to A, which allows us to expand (1.37) in powers of cor/c ... 

Fourier-transform infrared FTIR to the tip by the strong electrostatic field, and then ionized by electrons tunneling from the gas atoms into the tip. These ions, accelerated along radial trajectories by Coulomb repulsion, map out the variations in the electric field strength across the surface with atomic resolution, showing the surface topography. Broad-band IRAS experiments are performed and the IR adsorption Molecular structure... 

The foundation of the CoMFA approach lies in the fact that the interaction between the biotarget and organic ligand is usually non-covalent and substantially controlled by the shape of molecules. In addition, van der Waals and Coulomb forces in most cases provide an adequate description of non-covalent interactions within a molecular mechanics framework. Thus, the authors assumed that the biological action of compounds can be explained by the shape and electrostatic field of their molecules. 

Kroemer, R.T., Hecht, P. and Liedl, K.R. (1996). Different Electrostatic Descriptors in Comparative Molecular Field Analysis A Comparison of Molecular Electrostatic and Coulomb Potentials. J. Comput. Chem., 17,1296-1308. 

The variational iterative procedure to optimize wave function (6) is performed by an alternating process, which consists in first bringing to selfconsistency Wa in the electrostatic field of molecule B (in addition, of course, to its own field of electrons and nuclei), then Wb in the field of A, and so on until convergence is reached. The energy thus obtained contains the Coulomb interaction and polarization terms between A and B — i. e. the most important terms at large separation — and discards charge-transfer and dispersion effects. 

Volt The potential at a point in an electrostatic field is 1 volt, if 1 Joule of work per coulomb is done against electrical forces when a charge is brought from infinity to a point. A more usable definition is that / volt = / ampere flowing through a resistance of 1 ohm. E = 1 x R. Voltages are measured with voltmeters. 

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