Basicity Optical

Figure 7.15 (a) Enthalpy of formation of ternary oxides and nitrides from their binary constituent compounds as a function of the ratio of ionic potential [16]. Reprinted with permission from [16] Copyright (1997) American Chemical Society, (b) Gibbs energy of the oxide-sulfide equilibrium for group 1 and 2 metals at 1773 K as a function of the optical basicity of the metal. 

The problem of slight variation of h with metal ion has also been mentioned, but this is not serious because in the correlation we are seeking, it is changes in h which are important. Our present strategy is not to use the experimental values of h but to use ideal h parameters calculated from the constitution of the oxyanion medium and appropriate y parameters, along the same lines as in the calculation of ideal optical basicity (7 6). (It is also possible to evaluate an ideal h parameter for the oxide... 

This basicity concept (further discussed in Chapter 8) may be quantified by study of the spectra of probe ions such as Pb +, leading to values of optical basicity. These optical basicities can be correlated with polarizabilities, either macroscopic optical polarizabilities or the molecular-level polarizabilities, which influence the Auger parameter. 

As discussed in Chapter 5, data from both Auger spectroscopy and optical studies confirm a decreasing polarizability and/or optical basicity for silicate units as the degree of polymerization increases, consistent with the above interpretation. Polarizabilities (or better still, polarizabilities per O atom) have not yet been calculated for silicate polymers, nor have interaction energies of cation pairs such as Mg versus Fe with oxygens of various type yet been studied. 

Duffy, J. A., and M. D. Ingram (1976). An interpretation of glass chemistry in terms of the optical basicity concept. J. Noncryst. Solids 21, 373 10. 

D. L. Mills, Nonlinear Optics, Basic Concepts, Springer, Berlin, 1998. 

Figure 6.04. Activation energies for Na ion conducting glasses showing dependence on the optical basicity parameter A (After Hunter and Ingram, 1984).

Pb", Bi ions dissolved in a given compound compared to the same energies in CaO, which are taken as standards. Thus A, the optical basicity is defined as the ratio of the electron donating capacity of the compound to the electron donating capacity of CaO,... 

CaO. A of mixed oxides as in glass compositions are often expressed as weighted sums of the optical basicities of the constituent oxides, weighted by their equivalent fractions. 

Therefore the observed dependence of activation barriers on A suggests that during its actual motion in the glass, the cation may carry a positive charge less than its formal charge. Shastry et al. (1993) have shown that the optical basicity in principle should vary as a function of Mx, where x is molecular electronegativity of the given compound, Xi x v) = [Z A) They have also shown that when the same... 

Table 12.2 Optical basicities of individual oxides and a few oxyanion glasses (Duffy and Ingram, 1971 Baucke and Duffy, 1991).

Parameters of equation (1.2.9) for estimations of optical basicities in different ionic melts... 

Fig. 1.2.1. The dependence of the Hammett functions (2), the optical basicities A, obtained with the use of Bi(III) (3) and T1(I) metallo-indicators of some melts and superacids from the optical basicity obtained with the use of Pb(II) metallo-indicator (1).

J.A. Duffy and M.D. Ingram, Optical Basicity IV. Influence of Electronegativity on the Lewis Basicity and Solvent Properties of Molten Oxyanion Salts and Glasses, J. Inorg. Nucl. Chem. 37 (1975) 1203-1206. 

Orthoscopic examination with crossed polars is carried out first of all to determine the isotropism or the anisotropism of a sample. The polarization colors, the defects and variation in molecular orientation, and the orientation pattern or texture of liquid crystals are observed in this examination. With a heating stage the temperature of phase transition is also determined. In addition, with use of a compensator, the determination of vibration directions of the ordinary and extraordinary rays, the determination of relative retardation and birefringence are possible. In this section, the optical basics for orthoscopic observations are briefly outlined. The description of textures frequently observed for polymeric liquid crystals is given in Section 4.1.4. 

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