PLATON calculations

Kozik, M. Baker, L. C. W. Blue Electron Distributions in Diamagnetic Reduced Heteropolytungstates. Insights Concerning Conduction Pathways and Spin Coupling Patterns. 183W NMR Chemical Shift Calculations. In Polyoxometalates from Platonic Solids to Anti-retroviral Activity Pope, M. T. Muller, A., Eds. Kluwer Academic Publishers Dordrecht, 1994, pp 191-202. 

The corner diagonally opposite the pentacoordinate phosphorus is occupied by a tricoordinate phosphorus species, which is either monomeric metaphosphate (in the case of the reaction of a monoester) or a substituted derivative. Again, in the platonic sense it is easy to visualize metaphosphate as an ideal species, and it can be given reality by calculations (Sliznev et al., 1981) and by observations of species in the gas phase (Henchman et ah, 1985 Meyerson et al., 1984). However, the actual involvement of such a species in a stepwise substitution process in aqueous solution has not been demonstrated (Freeman et al, 1987). It is clear that such a species is highly electron-deficient, and it may be too reactive to exist as an intermediate (Guthrie, 1977). The quest for evidence in this system has produced elegant experiments that have provided much information about the nature of substitution at phosphorus in general. 

Many compounds are interesting because they represent novel geometric shapes that have not previously been identified in naturally occurring products. Tetrahedrane (26), in the shape of one of the Platonic solids, has not yet been synthesized,but theoretical calculations suggest that it might... 

That the water is not included in the crystallites is confirmed by a calculation on perfect crystals using Platon [57]. In o -PA6 the chains are ordered in... 

In addition, calculations of the void volumes of pure a-crystals indicate no solvent accessible areas. These calculations axe carried out with the program Platon [58], using a 1.2 A probe to scan the van der Waals surface of the polymer. The used van der Waals radii for C, N and O are 1.70A, 1.55 A and 1.52A respectively. Since no solvent accessible areas were found and no shift (within the experimental error) of the WAXD peak (200) was observed, we conclude that no water is located inside the crystallites of the Q-form. 

Fig. 6.1 Calix[6]arene structural features. Distances have been measured on tmergy minimized structures. Volumes have been calculated with PLATON software after obstructing smaii and/or large rim holes (Probe radius = 1.2 A Grid step = 0.2 A Atomic radii C = 1.70 A H = 1.20 A O = 1.52 A) [15]...

Solvent-accessible volume of the unit cell, calculated with PLATON [79], Angle (j> between the medium plane of the macrocycle and the SeC4Se unit(s). 

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