Phase, electrostatic potential formation

For compounds that are ionic rather than molecular solids, AHf can be calculated by appropriately combining the heats of formation of the gas phase ions (computed or experimental) with the lattice energy (converted to enthalpy [91]). We have developed formulas for lattice energies in terms of properties of the electrostatic potentials on the anions surfaces [92], for any of three possible cations NH4+, Na+ and K+. 

The multilayered character of acetonitrile adsorption creates a pseudo-stationary phase of significant volume on the surface, which acts as a suitable phase for the ion accumulation. In the low organic concentration region (from 0 to 20 v/v% of acetonitrile), studied ions show significant deviation from the ideal retention behavior (decrease in ion retention with increase in acetonitrile composition) due to the formation of the acetonitrile layer, and significant adsorption of the chaotropic anions was observed. This creates an electrostatic potential on the surface in which there is an adsorbed acetonitrile layer, which provides an additional retentive force for the enhancement of the retention of protonated basic analytes. When the dielectric constant is lower than 42 [167], this favors the probability of ion pair formation in this organic enriched layer on top of the bonded phase. 

Phase-transfer catalysis, 871-872, 901 a-Phellandrene, 1027 Phenacetin, 967 Phenanthrene, 408-409 Phenobarbital, 846 Phenol(s), 939-971 acidity of, 942-945, 962 electrostatic potential maps, 939, 942 formation of, in Claisen rearrangement,... 

As a consequence of the selective adsorption of ions with a higher affinity for the stationary phase than their counterions electrostatic theories assume the formation of a surface potential between the bulk mobile phase and stationary phase. The adsorbed ions constitute a charged surface, to which is attracted a diffuse double layer of strongly and weakly bound oppositely charged ions equivalent in number to the adsorbed surface charges to maintain electrical neutrality. Because of repulsion effects the adsorbed ions are expected to be spaced evenly over the stationary phase surface and at a concentration that leaves the properties of the stationary phase largely unaltered except for its electrostatic potential. The transfer of solutes from the bulk mobile phase to the... 

The spherical cell model was used early to examine the distribution of the small ions near a charged macroion and the thermodynamics of such systems. In the past, the model was used to investigate, e.g., the electrostatic potential and the small ion distribution [67- 74], the self-diffusion of coim-terions [75-78], the micelle formation of charged surfactants [79], and full phase diagrams of charged surfactant-water systems [80]. Many of those investigations were based on the PB equation, providing an approximate description of the model system. 

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. 

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