Quantum Chemical Topology

Overview

Quantum Chemical Topology (QCT) encompasses a family of methods that use the topology of scalar fields derived from the electron density—such as the gradient of ρ(r), the electron localisation function (ELF), or the non-covalent interaction (NCI) index—to partition molecular space into chemically meaningful regions (atoms, bonds, rings, cages).

The cornerstone of QCT is Bader’s Quantum Theory of Atoms in Molecules (QTAIM), which defines atoms as basin-like regions bounded by zero-flux surfaces of the electron density gradient. Critical points of ρ(r) identify bond, ring, and cage features, while integrated atomic properties (charge, kinetic energy, volume) carry well-defined quantum mechanical meaning.

Our Contributions

• Development of PROMOLDEN, a high-performance code for topological analysis of electron densities and pair densities.
• Systematic study of basin properties and their relationship to bonding descriptors.
• Extension of QCT frameworks to pair and reduced density matrices.

Key References

Selected publications from the group on quantum chemical topology are listed in the Publications section.