Starting from a BCP, the bond path corresponding to the steepest ascent path of electron density can be considered the most representative path of the interaction between atoms. The properties of the BCP are closely related to the characteristics of the interaction. It is important to note that methods like IGMH, IRI, and NCI are never merely graphical extensions of QTAIM analysis, as they can reveal many notable interactions that QTAIM cannot study, such as many intramolecular Hbonds. For detailed relevant mathematical analysis and discussion, see Ref. .