Non-covalent interactions from a Quantum Chemical Topology perspective

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Chemical Topology

Background:

• Quantum Topological Atom In Molecule (QTAIM) is an interpretational quantum chemistry method.
• QTAIM, alongside Interacting Quantum Atoms (IQA) and Electron Localisation Function (ELF), forms the broader Quantum Chemical Topology (QCT) approach.
• Current focus is on QCT's implications beyond non-covalent interactions, stemming from the space-filling nature of topological atoms.

Purpose of the Study:

• To explore novel ideas arising from the space-filling nature of topological atoms within QCT.
• To discuss the impact of these ideas on interatomic interactions, including non-covalent ones.
• To introduce a new computational method for analyzing molecular assembly energetics.

Main Methods:

• Utilizing the mathematical framework of Quantum Chemical Topology (QCT).
• Outlining the architecture of the FFLUX force field, based on QCT principles.
• Developing and applying the Relative Energy Gradient (REG) method for energetic analysis.

Main Results:

• The study proposes new concepts derived from space-filling topological atoms.
• The Relative Energy Gradient (REG) method is introduced to identify influential molecular fragments.
• The REG method provides insights into the balance of atomic energies in covalent and non-covalent interactions.
• Concerns regarding the interpretation of bond critical points in non-covalent interactions are highlighted.

Conclusions:

• The space-filling nature of topological atoms opens new avenues in Quantum Chemical Topology.
• The Relative Energy Gradient (REG) method is a valuable tool for understanding molecular assembly energetics.
• Further investigation into QCT and its applications, including bond critical points, is warranted.