Chemical Bond, from the Quantum Theory of Atoms in Molecules


Dr. Cina Foroutan-Nejad


Currently, bonding analysis of molecules based on the Quantum Theory of Atoms in Molecules (QTAIM)
is popular; however, “misinterpretations” of the QTAIM analysis are also very frequent. In this
contribution the chemical relevance of the bond path as one of the key topological entities
emerging from the QTAIM’s topological analysis of the one-electron density is reconsidered. The
role of nuclear vibrations on the topological analysis is investigated demonstrating that the bond
paths are not indicators of chemical bonds. Also, it is argued that the detection of the bond paths
is not necessary for the “interaction” to be present between two atoms in a molecule. The
conceptual disentanglement of chemical bonds/interactions from the bonds paths, which are
alternatively termed “line paths” in this contribution, dismisses many superficial inconsistencies.
Such inconsistencies emerge from the presence/absence of the line paths in places of a molecule in
which chemical intuition or alternative bonding analysis does not support the presence/absence of a
chemical bond. Moreover, computational QTAIM studies have been performed on some “problematic”
molecules, which were considered previously by other authors, and the role of nuclear vibrations on
presence/absence of the line paths is studied demonstrating that a bonding pattern consistent with
other theoretical schemes appears after a careful QTAIM analysis and a new “interpretation” of data
is performed.