Anionic group theory

This review gives a brief presentation of the basic concepts and calculation methods of the "anionic group theory" for the NLO effect in borate crystals. On this basis, boron-oxygen groups of various known borate structure types have been classified and systematic calculations were carried out for microscopic second-order susceptibilities of the groups. 

In the following part we will give a brief description of the "anionic group theory" for the NLO effects in crystals, including the basic concepts and calculation methods adopted. In the next section we will discuss how to use this theoretical model to develop new UV NLO crystals in the borate series. Finally, the measurements and characteristic features of the NLO properties of these new borate crystals will be discussed. 

We now proceed to apply our anionic group theory to a systematic discussion of the NLO effects in borate crystals. The extension of our investigation into the NLO effects of borate crystals has great practical significance in two respects. On the one hand, most borate crystals are transparent far into the intermediate UV region and occasionally even farther because of the large difference in the electro-... 

If one uses the anionic group theory to analyze these deficiencies in view of the structure of BBO, it is not difficult to understand that the origin of all these disadvantages is the (B306) planar six-memberring group itself[29,30 ]. ... 

Calculations of birefringences of the crystals using anionic group theory",... 

Anharmonic oscillator-molecular orbital theory connection anharmonic energy profile, 97,98/ two-orbital calculation, 96-97,98/ Anharmonic springs, nonlinear polarizabilities, 90 Anionic group theory assumptions, 364-365... 

The next step to reach to our aims is to determine the localized molecular orbitals of the anionic group. Of course, there are many methods available for the calculations of molecular orbitals in our theory, such as the various approximation methods and even the recently developed Dv-Xa method discussed in quantum chemistry. But, in view of the nature of the basic assumptions in our theory, the CNDO approximation seems to be suitable for calculations of SHG coefficients when the anionic groups consist of elements from the first, second and third families in the periodic table. EHMO type approximations are suitable for other elements, particularly if transition metal elements take part in the ionic groups or molecules. It is not necessary to use higher approximations. 

Here we summarize the key developments with emphasis on the post-1985 period and the role of the carbon surface. Bansal et al. [35] have grouped the postulated mechanisms as follows (1) reduction theory (2) ion-pair adsorption theory (3) aurocyanide anion adsorption theory and (4) cluster compound formation theory. 

No individual cation can hold the chains together permanently, because its lifetime in the polymer domain is short, and this mechanism is therefore quite different from the simple ionic bridge or simple chelation model. This distinction is insisted on, because polyelectrolyte theory can lead to important predictions concerning, for example, the effect of a change of distribution of anionic groups... 

Apply the simple LCAO method (use group theory) to the cyclopropenyl cation, radical, and anion. Calculate DEtt, pij, and qi. Sketch out the molecular... 

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