The NG-QTAIM Interpretation of the Chemical Bond

In this chapter we present the NG-QTAIM representation of the chemical bond, the bond-path framework set $$\mathsf{B}$$ . The bond-path framework set $$\mathsf{B}$$ is constructed from the e1 and e2 eigenvectors, in contrast to conventional (scalar) QTAIM that is only constructed using the e3 eigenvector. Consequently, $$\mathsf{B}$$ is much more sensitive to changes in the distribution of the total electronic charge density distribution ρ(r) than is the case for the QTAIM bond-path. In Sect. 4.1 we outline the construction of the bond-path framework set $$\mathsf{B}$$ and briefly include some of the possible geometrical properties of $$\mathsf{B}$$ . The procedure to calculate the precession $$\mathsf{K}$$ of $$\mathsf{B}$$ is described in Sect. 4.2. In Sect. 4.3 we consider the applications of $$\mathsf{B}$$ that highlight the sensitivity to changes in ρ(r). This includes the infrared active modes of benzene in Sects. 4.3.1–4.3.3. The treatment of strained and unusual bonding environments is accommodated in Sect. 4.4. The provision for including multi-electronic statesMulti-electronic state is detailed in Sect. 4.5. The summary of the chapter is presented in Sect. 4.6 by outlining benefits, limitations and suggestions for further investigations of the ideas introduced. Further reading materials are provided in Sect. 4.7.