This code implements the APEPM model found on chemrxiv, and is intended to ideally be used either as a pre-QM screening method to see if bonds are geometrically possible (not energetically)(if overlap radius = 0, then there can be no bond), or see if a bond is possible at all based on distance between electron radii of 2 atoms. APEPM model paper available here: https://doi.org/10.26434/chemrxiv-2026-9swcr
This model and paper relies on AREECM notation, the code already comes with the digital AREECM dictionary, but for the "+1" rule seen here that applies to AREECM notation, for a better understanding of AREECM, the AREECM paper can be found here on chemrxiv: https://doi.org/10.26434/chemrxiv-2025-jq84z-v3, and additional educational resources can be found on youtube: https://youtu.be/Zj-MEX8jEus (How to read AREECM notation) and: https://youtu.be/6NM0zsfH-Jg (How to convert Integer electron notation to AREECM Notation (Step-by-Step)), and finally a video on how to use APEPM: https://youtu.be/fyqJNUVcqDg
Deterministic identification of infeasible or highly strained bonds based solely on geometry
Millisecond-scale assessment for molecules, clusters, and periodic fragments
Closed-form, non-iterative calculations with no SCF or convergence tuning
Use as an interpretable constraint or weighting layer inside custom energy models
Real-time generation of orbital-overlap visualizations (e.g., Au···Au metallophilic contacts, U=O actinyl bonds, metal–oxo motifs) without requiring QM density cube files
APEPM separates geometric admissibility from energetic favorability, providing structural context and reducing wasted downstream computation in high-throughput industrial workflows.
The repository and associated papers are released under CC BY-NC 4.0. Commercial deployment or integration requires a dedicated license agreement from the owner.