A first step towards quantum energy potentials of electron pairs

Area of Science:

• Quantum chemistry
• Computational materials science
• Chemical physics

Background:

• Developing accurate quantum force fields is crucial for molecular simulations.
• Existing models often struggle with electron delocalization and non-conventional bonds.
• Topological analysis offers a novel approach to understanding electron behavior.

Purpose of the Study:

• To construct a quantum force field for electron pairs in direct space.
• To analyze the energetic contributions (electrostatic, kinetic, exchange-correlation) of electron pairs during bond stretching.
• To develop a real-space energy model applicable across diverse bonding types.

Main Methods:

• Utilized topological tools: Interacting Quantum Atoms (IQA) and Electron Localisation Function (ELF).
• Analyzed the dependence of electron pair energies on bond stretching.
• Employed elementary models like the homogeneous electron gas for correlation analysis.

Main Results:

• Established simple correlations between electron pair energies and bond stretching.
• Developed an energy model valid for homopolar, polarized, and non-conventional bonds.
• Found exchange-correlation contributions to be negligible in typical Lewis structures but significant for delocalized and lone pairs.

Conclusions:

• The study presents a novel, real-space approach to quantum force fields including exchange-correlation terms.
• The findings justify the success and delineate the limitations of the classical Bond Charge Model (BCM).
• This framework paves the way for rigorous, quantitative energy models based on ELF topology.