Topological analysis of experimental densities

Topological analysis of the total density has a considerable advantage over the use of the deformation densities in that it is reference-density independent. There is no need to define hybridized atoms to analyze the nature of covalent bonding, and the ambiguity when using the standard deformation density, noted above in the discussion on propellanes, does not occur. 

For analysis of experimental results, the static model density must be used to eliminate noise, truncation effects, and thermal smearing. Some caution is called for, because the reciprocal space representation of the Laplacian is a function of F(H) H2, and thus has poor convergence properties.2 This difficulty is only partly circumvented by use of the model density, as high-resolution detail may be quite dependent on the nature of the model functions, as is evident in the experimental study of the quartz polymorph coesite discussed in chapter 11. 

The values of the Laplacian V2pb and its components z1i2,3 obtained in the 

2 See Table 8.1 for the dependence of derived properties on the power of the magnitude of scattering vector H. 

R bond length Rx distance of bond critical point from first atom pb density at bond critical point. Units are A, eA and eA-5, respectively. 

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