Information Gain from Density-Based Reactivity Theory Reveals Charge-Shift Bonding in Real Space
Xiaoyan An1, Tian Lu2, Tingzhen Chen1
1The State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, China.
The Journal of Physical Chemistry. A
|July 22, 2026
Summary
Charge-shift bonding, a new chemical bonding type, is identified using information gain (IG). This method quantizes resonance effects in electron density, bridging valence bond and density functional theories for chemical bonding analysis.
Area of Science:
- Quantum Chemistry
- Chemical Bonding Theory
- Computational Chemistry
Background:
- Charge-shift bonding (CSB) challenges traditional covalent-ionic paradigms.
- Existing CSB identification relies on separate valence bond theory (VBT) or molecular orbital theory (MOT) analyses.
- A unified, quantitative link between resonance energy and electron density is lacking.
Purpose of the Study:
- Introduce a unified, real-space descriptor for chemical bonding.
- Connect resonance effects in VBT with electron density analysis in DFT.
- Provide a robust diagnostic for charge-shift bonding.
Main Methods:
- Utilize information gain (IG) from density-based reactivity theory within DFT.
- Define IG as Kullback-Leibler divergence between actual and reference electron densities.
- Employ covalent and ionic reference densities to analyze bonding characteristics.
Main Results:
- Negative IG indicates regular covalent bonds when using a covalent reference density.
- Positive IG signals charge-shift bonding character.
- A sign flip of IG between covalent and ionic references robustly diagnoses CSB, revealing resonance competition.
Conclusions:
- Information gain (IG) provides a unified real-space measure of chemical bonding.
- IG directly links resonance in VBT with DFT-based electron density descriptors.
- This approach offers a continuous transition between bonding regimes and a robust CSB diagnostic.
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