Point charge electrostatic model

Price S L, R J Harrison and M F Guest 1989. An Ab Initio Distributed Multipole Study of the Electrostatic Potential Around an Undecapeptide Cyclosporin Derivative and a Comparison with Point Charge Electrostatic Models. Journal of Computational Chemistry 10 552-567. 

How to Determine the Crystal-Field Parameters 2. The Point Charge Electrostatic Model... 

In order to avoid overparametrization, we can use the point charge electrostatic model (PCE model) [19, 20], in which N ligands are represented by their point charges (Zt). The Hcf generated by a charge distribution can be written in its most primitive form as a sum of Coulomb fields created by the charges. The Aq CF parameters can then be calculated by the following expression ... 

The effective CF models, intended to include covalence effects via effective charges and shielding parameters [46] (superposition model [47], effective charge model [48], simple overlap model [49, 50]), keep the radial (M-L distance) dependence of the CF parameters as in the simple (point charge) electrostatic model. Dedicated studies have shown, however, that the radial dependence of these parameters deviates strongly from the latter for the whole series of lanthanide ions [51, 52]. 

Kibler, by a comparison of the point charge electrostatic model and the angular overlap model, has shown the equivalence between these two models he has given some simple relations between intrinsic parameters for a series of ligands and antibonding radial contributions e (X = a, 7r, 8, ) (Table 17). Kibler s I are different from our A (the basis is not the same). In Table 17 transformation formulas will be noticed. Kibler s eCT is besides seven times greater than the a found by Jorgensen s method. 

Kibler, M. R. (1970) Comparison between the point charge electrostatic model and the model. Chem. Phys. Letters 7, 83. 

The contribution of 0th rank is called the point charge contribution. It was the only one included in the first version of the model which was, for this reason, designated as the point charge electrostatic model (PCEM). This contribution is written as ... 

The point-charge electrostatic model is useful in illustrating how symmetry influences the signs of the crystal field parameters B. However, it does not usually result in accurate determinations of their magnitude and therefore other methods have been developed that lead to a better estimation. One such approach is based on the angular overlap model AOM developed and expanded to the/elements by Jprgensen [45]. Another approach is the simple overlap model SOM, proposed by Malta [46]. 

PCEM point charge electrostatic model Ph phosphorescence... 

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