Electrostatic potentials surface, variability

The macroscopic property of interest, e.g., heat of vaporization, is represented in terms of some subset of the computed quantities on the right side of Eq. (3.7). The latter are measures of various aspects of a molecule s interactive behavior, with all but surface area being defined in terms of the electrostatic potential computed on the molecular surface. Vs max and Fs min, the most positive and most negative values of V(r) on the surface, are site-specific they indicate the tendencies and most favorable locations for nucleophilic and electrophilic interactions. In contrast, II, a ot and v are statistically-based global quantities, which are defined in terms of the entire molecular surface. II is a measure of local polarity, °fot indicates the degree of variability of the potential on the surface, and v is a measure of the electrostatic balance between the positive and negative regions of V(r) (Murray et al. 1994 Murray and Politzer 1994). 

The variances indicate the variabilities, or ranges, of the positive, the negative and the overall electrostatic potentials on the molecular surfaces. They are particularly sensitive to the extrema, Vs,max and Vs,min, due to the terms being squared. This also means that they may be much... 

Our experience has been that the computed electrostatic potentials Vs(r) on the surfaces of all-carbon tubes are generally weakly positive and rather bland, with little variability. Vs(r) is usually less than lOkcal/mole. Slightly negative regions are most likely to be found on the outer surfaces of the caps. The total variance, ofot, tends to be less than 20(kcal/mole)2 this is typical of alkane and aromatic hydrocarbons, but much less than most other organic molecules, for which <72t is normally 10CF300 (kcal/mole)2.46,47... 

Early MEP-based parameters considered included surface area (A), If, and v. Flere II is a measure of local polarity, and is a measure of electrostatic interaction tendency. Larger values imply larger charge separation leading to greater electrostatic interaction. Electrostatic interactions are also described by v, which is a measure of electrostatic balance. The three charge related variables are defined in terms of the surface electrostatic potential difference, 8U at the ith point, Eq. [33],... 

In all cases, the variability for the PDQC charges in Table 2 is highest for the central carbon atom. As Woods et al. note, the exposure of the van der Waals surface of the methanol carbon atom is quite limited. As a result, the electrostatic potential will be more sparsely sampled in this region and perhaps therefore will not be as well described by the final parameters. Classical electrostatics is likely playing a role here as well. Classically, all the charge on a charged object is found on the surface of the object. Because class III charge... 

Now eUWR is still fixed by the Nemst Eq. 7.16 but w are variables. They can change due to the spillover of ions which can now establish a constant electrochemical potential not only in the solid electrolyte but on the gas exposed electrode surfaces as well. They will change in such a way as to minimize the excess electrostatic energy of the system... 

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