Bond critical point, AIM definition

The second very important point in AIM theory is its definition of a chemical bond, which in the context of gradient paths, is straightforward. In fact, some gradient paths do not start from infinity but from a special point, the bond critical point, located between two nuclei. 

The theory of AIM allows one to study the concept of chemical bond and the bond strength in terms of electron density distribution function [6, 193]. It exploits the topological features of electron density and thereby a definition of chemical bonding through bond path and bond critical point (BCP). A BCP (it is a point at which gradient vector vanishes, Vp(r) = 0) is found between the 

This correlation is illustrated in Figure 1.44. Polarizability is related to softness. Expressed as it is proportional to softness, approximated by 2/(IP-EA). DFT also suggests explicit definitions of covalent and van der Waals radii. The covalent radius in the AIM context is defined by the location of the bond critical point 

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