Shell topological compound

ABSTRACT. A Lennard-Jones potential is used to derive for-mulaefor the potential of interaction between shell macro-molecules and gas atoms. Calculations are carried as far as thespherlcal symmetry approximation. The potential of interaction determines the stability of a shell topological compound. When the distance R between a shell molecule and a gas atom is equal the radius 1 of the outer shell, the potential is the highest and determines a barrier, which must be lower than an energy of the trapped / by the shell molecule / atom to be released. 

The potential can be used in the calculation of the partition function and then in thecUtermlnatlon of the free energy of the system. However, the potential Itself especially that of the outer shell f a shell molecule is Important and determines the stability of a shell topological compound which is a topological isomer of two... 

With the topological analysis of the total charge density, the distinction between a covalent and a closed-shell ionic interaction can be based on the value of the Laplacian and its components at the bond critical point. Such an analysis will be most conclusive when done on a series of related compounds, analyzed with identical basis sets, as the topological values of the model density from experimental data have been found to be quite dependent on the choice of basis functions. 

Cyclazinylium salts (233), which following MO considerations should be unstable antiaromatic compounds, have not been described so far. Topologically equivalent -systems containing two additional electrons, however, appear to be closed shell systems and some compounds corroborating this expectation have been prepared. 

Atom-Centered Fragments (ACE) consist of a single central atom surrounded by one or several shells of atoms separated from the central one by the same topological distance. This type of structural fragments was introduced in the early 1950s by Tatevskii, " and then by Benson to predict some physicochemical properties of organic compounds in the framework of additive schemes. 

The studies presented here deal with the coordination of cobalt atoms in cobalt aluminophosphates (CoAPOs). The compounds investigated include those of CHA topology (CoMnAPO-34) [51] and of SOD topology [42].In the case of the CoMnAPO, a perfect fit to the filtered EXAFS function of the first coordination shell is obtained with four oxygen atoms at a distance Rco-o of 1-93 A. This result is consistent with the presumed incorporation of the Co atoms into the alu-minophosphate framework [51]. 

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