From quantum fragments to Lewis structures: electron counting in position space.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Chemical Bonding Theory

Background:

• Traditional methods for determining Lewis structures often rely on orbital-based analyses.
• Existing real space methods may struggle with complex many-electron correlations.
• The adaptive natural density partitioning (AdNDP) algorithm offers a foundation for density-based analysis.

Purpose of the Study:

• To develop a novel electron counting technique for generating Lewis structures.
• To reformulate the AdNDP algorithm in position space for broader applicability.
• To provide chemically intuitive Lewis descriptions from real space wavefunctions.

Main Methods:

• Reformulation of the AdNDP algorithm using domain-averaged cumulant densities in position space.
• Integration with the quantum theory of atoms in molecules (QTAIM) for basin averaging.
• Application to both single- and multi-determinant wavefunctions.

Main Results:

• A robust electron counting method yielding n-center, two-electron orbitals.
• Successful generation of dominant Lewis structures for molecular systems.
• Demonstration of orbital invariance and chemical intuition in position space descriptors.

Conclusions:

• The proposed real space method provides accurate and intuitive Lewis structures.
• This technique offers a competitive alternative to Natural Bond Order (NBO) analysis.
• It overcomes limitations associated with orbital-based methods and biases.