Electrostatic interaction pairs

The leading temi in the electrostatic interaction between a pair of linear, quadmpolar molecules, such as HCCH and CO2 is... 

If the long-range mteraction between a pair of molecules is treated by quantum mechanical perturbation theory, then the electrostatic interactions considered in section Al.5.2.3 arise in first order, whereas induction and dispersion effects appear in second order. The multipole expansion of the induction energy in its fill generality [7, 28] is quite complex. Here we consider only explicit expressions for individual temis in the... 

Although electrostatic interactions between pairs of molecules may be weak in many cases, a consequence of their long-range nature is that in large systems the energy due to electrostatic interactions must be calculated between all the pairs of the system and thus will dominate all other interactions. It is essential to include them. 

Mesomerism involving polarized and nonpolarized contributing enamine forms influences the enamine s spectral properties and chemical reactivity. For mesomerism to be present, a planar arrangement is required for the three atoms of enamine grouping and the five atoms immediately bound to this system. If this condition is not fulfilled, full interaction of the tt electrons of the double bond with the free electron pair on the nitrogen atom is impossible. Enamines in which mesomerism is inhibited do not show the properties characteristic of enamines, and only the mutual electrostatic interaction of the double bond and lone electron pair of the nitrogen atom can be observed. Such steric hindrance of mesomerism occurs mainly in polycyclic systems. 

A number of intermolecular potentials have been developed over the years that treat molecules as collections of point charges. The intermolecular electrostatic potential is taken as a sum of the mutual electrostatic interaction of these point charges, summed over interacting pairs of molecules. Occasionally, extra van der Waals terms are added to the potential. 

A common feature of many mesogenic molecules is the presence of polar substituents and aromatic cores [3]. The electrostatic interactions between such groups can be incorporated into a molecular potential with the addition of dipolar and quadrupolar terms, respectively. Rather than represent these permanent electrostatic interactions by using a model in which a charge distribution is scattered over the surface of the molecule, it is very common to use one (or more) point multipoles [2,29]. Thus for an electrostatic Gay-Berne model, the pair potential is given by the sum... 

The structures of phases such as the chiral nematic, the blue phases and the twist grain boundary phases are known to result from the presence of chiral interactions between the constituent molecules [3]. It should be possible, therefore, to explore the properties of such phases with computer simulations by introducing chirality into the pair potential and this can be achieved in two quite different ways. In one a point chiral interaction is added to the Gay-Berne potential in essentially the same manner as electrostatic interactions have been included (see Sect. 7). In the other, quite different approach a chiral molecule is created by linking together two or more Gay-Berne particles as in the formation of biaxial molecules (see Sect. 10). Here we shall consider the phases formed by chiral Gay-Berne systems produced using both strategies. 

This concept is due to Bjerrum, who in 1926 suggested that in simple electrolytes ions of the opposite charge could associate to form ion-pairs (Szwarc, 1965 Robinson Stokes, 1959). This concept of Bjerrum arose from problems with the Debye-Huckel theory, when the assumption that the electrostatic interaction was small compared with IcTwas not justified. 

The first ideas concerning a role of pairwise electrostatic interaction between ions were advanced in 1924 by Vladimir K. Semenchenko. A quantitative theory of the formation of ion pairs was formulated in 1926 by Niels Bjerrum. 

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