Points-on-a-sphere models

Figure 4.4 The points-on-a-sphere model. The most probable arrangements of two, three, four, five, and six points on the surface of a sphere that maximizes their distance apart.

A detailed discussion of geometry in terms of the points-on-a-sphere model. 

Calculations based on the 1/r" (n = 6) repulsion law for the points-on-a-sphere model in which the points can represent either electron pairs or ligands have shown that the pentago-... 

Figure 9.28 (a) Points-on-a-sphere model of a square an-liprism. (b) The square antiprism geometry of the IFg2- ion. 

This force field has also been used to explain the bent geometry of [M((CH3)5C5)2] complexes (M = calcium, strontium, barium, samarium, europium, or ytterbium). However, Hollis et al. set the ring carbon—dummy-dummy—ring carbon dihedral (as described by Doman et al.44) and dummy— metal-dummy bending force constants to zero. Thus, the force field is a points-on-a-sphere model. As one might expect, the calculated structures were... 

You may now want to further modify your Co —N force field. One instmctive possibility is to replace the modified points-on-a-sphere model (1,3-interactions around the metal center, perturbed with a multiple harmonic potential, see Sections 17.9 and 3.2.2) by a more conventional angle function. To do this, you have to go back to the forcefield-shcfw section and navigate to the Junctions subtab, where you can select the multiple harmonics option, that is, model the angular geometry without 1,3-non-bonded interactions. 

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