Ionic polarisability

Ionic Polarisability Polarisability of an atom is the ability of the applied electric field to distort the electric cloud and thus induce an electric dipole moment. 

Long-wavelength refractive index [40,41] suggests a high frequency dielectric constant ex = a2 = 8.4, a value supported by recent measurement [42] and ab initio calculation [43], Ionic polarisability makes a significant contribution at low frequencies where, although measurement is presently inhibited by a high conductivity, s0 15 is recommended [43],... 

Figure 11.4 The effects of an electric field tronic polarisation, (b) ionic polarisation and (c) orienta tional polarisation dipoles are shown as arrows...

Lorentz-Lorentz equation. Equation (11.11), will yield the electronic polarisability of the material. Hence, by difference, the ionic polarisability can be estimated. 

The observed bulk polarisabUity of a solid, a, will arise from the sum of a number of separate terms such as electronic polarisability, ionic polarisability and so on. As the total polarisability of a material is made up several contributions, the relative permittivity, r, can also be thought of as made up from the same contributions. In a static electric field, all the various contributions will be important and both a and r will arise from electrons, ions, dipoles, defects and surfaces. 

The eutectic composition of LiF-CaF2 (80.5 to 19.5 mol%) were simulated by MD. The interaction potential used in those simulations was calculated with the PIM which consists of a Born-Mayer pair potential forming together with an ionic polarisation [11]. The simulations were performed on a box containing 239 F , 39 Ca " and 161 Li+ ions, and for temperatures ranging between 770 and OtWC. 

Ionic Polarisability — Self Consistent Mean-Field Theory... 

The BO description is in principle well adapted to incorporate the zero-frequency ionic polarisability and account for the coupling between charges, fixed and induced dipoles. A polarisable particle (solvent or ion) responds to the applied electric field exerted by its neighbours with an induced dipole, which will then exert a new field in the neighbourhood, and so on. The problem of the polarisable systems is that the interaction is no more pair-wise additive. The 2 -body problem can be explicitly treated in numerical simulation (with difficult and rather time-consuming iterative procedure at each configuration) but is not adapted to integral equations... 

Removal of the inconsistency in the manner Ninham, Bostrom and co-workers have described in a series of papers goes part of the way to a resolution, but only at the level of the primitive model. More is involved once the molecular nature of the solvent is taken into account. Ionic polarisability is combined at the same level with electrostatics to determine local induced water structure around ions. That is a key determinant of hydration, and of so-called ion specific Gurney potentials of interactions between ions due to the overlap of these solute-induced solvent profiles so too for ionic adsorption at interfaces. The notions involved here embrace quantitatively the conventional ideas of cosmotropic, chaotropic, hard and soft ions. Some insights into this matter can be obtained via the alternative approach of computer simulation techniques of Jungwirth etal. But the insights are hamstrung so far by a pragmatic restriction that limits... 

HHDMA are highly soluble in water and caimot be extracted into an organic solvent. It is more likely that these metal particles are stabilised by a double layer of HHDMA, where the outer shell of the colloidal particle exists of ammonium functionalities of the second HHDMA layer. An inverted monolayer, in which the polar functionalities stick out into the aqueous solution while the apolar alkyl chains interact with the metal surface, seems unlikely to us. Although a fully reduced metal surface in itself is not ionic, polarisation by ionic species is possible. In organic solvents, XANES studies on colloidal suspensions indicate the interaction of the reduced metal surface with the ionic moiety of alkyl ammonium stabilisers. ... 

There are many AC and DC techniques for probing the transport of charged and neutral species. Among them, we can refer to the electrolysis method, the concentration cell techniques, and the ionic polarisation cell technique. 

The ionic polarisation cell technique involves transport under a chemical potential and electrical gradient and, therefore, includes the contributions of both charged and neutral species. The AC procedure has been suggested by Sorensen and Jacobsen (1982) and is based on the theory of MacDonald (1973,1974) which involves analysis of the impedance spectra of the symmetric cell MIP MXIM. 

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