A Fragment-Based Mechanistic Potential for Noncovalent Systems: Combining Conceptual DFT and Quantum Chemical Topology Domains
Year: 2026
Type: preprint
Abstract: Within a framework combining conceptual Density Functional Theory (cDFT) with the computational efficiency of the quantum chemical topology (QCT) description of matter, we introduce a mechanistic potential designed for the fast exploration of intermolecular potential-energy surfaces between rigid molecular fragments. The proposed strategy deliberately retains only a minimal set of physically interpretable contributions, namely electrostatics, charge transfer, and dispersion. All electronic properties are evaluated once for the isolated rigid fragments and subsequently propagated using the Kabsch algorithm during their relative translations and rotations, so that the potential energy depends only on the six intermolecular degrees of freedom. The proposed workflow is illustrated using a set of noncovalent and donor-acceptor complexes displaying different degrees of directionality and intermolecular overlap. In the long-range regime, the effective potential mimics a substantial part of the orientational selectivity and correctly identifies the main low-energy regions and interaction-energy minima. This behavior is illustrated for weakly bound systems, hydrogen-bonded and donor–acceptor complexes, σ-hole interactions, the guanine–cytosine pair, and the CO2 molecule confined within a (H2O)20 clathrate cage. Deviations from reference DFT profiles become more pronounced at shorter intermolecular separations, where Pauli repulsion and polarization contributions, which are not explicitly included in the model, become significant. The resulting approach therefore provides a fast, computationally inexpensive, and physically interpretable tool for the prescreening and exploration of intermolecular potential-energy surfaces, allowing favorable orientations and low-energy structures to be identified prior to more demanding electronic-structure calculations. More generally, this mechanistic strategy may provide a useful route for the modeling and exploration of increasingly complex non-covalent molecular and supramolecular systems.
Source: ChemRxiv
Authors: Julien Pilmé, Julien Pilme
Institution: Sorbonne Université
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220359586