WFX Molecular Fragment References for Hirshfeld Charge-Transfer Analysis in Non-Covalent Complexes
Jorge Garza1, Rubicelia Vargas1
1Departamento de Química, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana Iztapalapa, Iztapalapa, México.
Journal of Computational Chemistry
|July 29, 2026
Summary
A new fragment-based Hirshfeld scheme using molecular WFX files provides a more accurate analysis of intermolecular charge transfer. This method reduces fragment-charge magnitudes, offering chemically meaningful insights into non-covalent interactions.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Molecular Interactions
Background:
- Accurate analysis of intermolecular charge transfer is crucial for understanding non-covalent interactions.
- Traditional Hirshfeld partitioning methods can be limited by the choice of reference densities.
Purpose of the Study:
- To introduce and evaluate a novel fragment-based Hirshfeld scheme utilizing molecular WFX files for reference density reconstruction.
- To compare the performance of atomic WFX references versus molecular WFX fragment references in partitioning electron density.
- To provide a chemically meaningful, density-based reference for analyzing intermolecular charge transfer.
Main Methods:
- Development of a fragment-based Hirshfeld scheme using WFX files of isolated fragments.
- Reconstruction of full complex electron density from WFX files.
- Partitioning of electron density using atomic WFX references or molecular WFX fragment references on a shared integration grid.
- Application to water clusters and S66 benchmark set complexes (hydrogen-bonded, donor-acceptor, π-stacked, symmetric, dispersion-dominated).
Main Results:
- Molecular WFX fragment references yield substantially smaller fragment-charge magnitudes compared to atomic references across various computational methods (DFT, CCSD).
- Significant reductions (75%-90%) in fragment charge were observed for hydrogen-bonded and donor-acceptor complexes.
- Symmetric and dispersion-dominated systems showed near-zero net integrated fragment charge.
- The WFX fragment references capture charge redistribution relative to isolated monomers, unlike atomic references.
Conclusions:
- The proposed fragment-based Hirshfeld scheme with molecular WFX references offers a chemically meaningful approach to density partitioning.
- This method accurately quantifies intermolecular charge transfer in non-covalent complexes.
- It provides a superior reference for analyzing electronic redistribution in molecular interactions.
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