A reliable and efficient resonance theory based on analysis of DFT wave functions

Area of Science:

• * Quantum Chemistry
• * Theoretical Chemistry
• * Computational Chemistry

Background:

• * Traditional resonance theory faces methodological challenges and limited applicability.
• * Molecular Orbital (MO) methods are currently more prevalent for quantitative bonding analysis.
• * Existing resonance theory approaches struggle with large molecules and complex bonding.

Purpose of the Study:

• * To develop an efficient and broadly applicable quantitative resonance theory.
• * To enable accurate bonding analysis for large molecules and intricate electronic systems.
• * To provide a robust alternative to existing molecular orbital methods.

Main Methods:

• * Expanding the Density Functional Theory (DFT) wave function using a complete set of Lewis structures.
• * Rigorously separating resonance subsystems with localized MOs.
• * Employing a novel projection-weighted symmetric orthogonalization for resonance contributor weighting.

Main Results:

• * The proposed method effectively handles large molecules, nonplanar π-conjugate systems, and mixed σ/π bonding.
• * The new weighting scheme overcomes drawbacks of previous methods.
• * Applications to benzene, naphthalene, and chlorobenzene demonstrate basis set and Lewis set independence.

Conclusions:

• * The developed quantitative resonance theory provides a powerful tool for chemical bonding analysis.
• * It offers unique insights into hydrogen bonding, π substituent effects, and reaction mechanisms.
• * This method enhances the understanding of electronic structure and chemical behavior.