On bond-critical points in QTAIM and weak interactions

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• The Quantum Theory of Atoms in Molecules (QTAIM) utilizes bond critical points (BCPs) to characterize chemical bonds.
• BCPs are derived from the topology of the electron density scalar field within molecules.

Purpose of the Study:

• To investigate the fundamental origins of bond critical points (BCPs) within the Quantum Theory of Atoms in Molecules (QTAIM).
• To assess the suitability of BCPs and their associated bond paths for identifying chemical bonds and intermolecular interactions.

Main Methods:

• Analysis of molecular topology and symmetry.
• Application of the Poincaré-Hopf relationship to scalar fields.
• Examination of BCP formation under external influences like polarizing fields or added atoms.

Main Results:

• Bond critical points (BCPs) are demonstrated to be a direct consequence of molecular topology, symmetry, and the Poincaré-Hopf theorem.
• BCPs can be artificially induced by external factors such as polarizing fields or the addition of non-bonded atoms.
• The presence of a BCP does not exclusively indicate a chemical bond or attractive intermolecular interaction.

Conclusions:

• Bond critical points (BCPs) and their associated bond paths may not be reliable indicators for identifying chemical bonds.
• The findings suggest caution when using BCPs to define or confirm attractive intermolecular interactions.
• Molecular topology and symmetry are the primary determinants of BCP existence in QTAIM.