169339 20260225105429.0 doi 10.1039/d5dt02699g sideral 148325 ART-2026-148325 eng Pardos, Jorge Universidad de Zaragoza Beyond bond distances: a purely geometrical descriptor correlating with covalency-related bonding terms 2026 Quantifying covalency remains a central challenge in understanding chemical bonding. Traditional distance–bond strength correlations often fail in diverse bonding regimes, and most existing metrics require computationally demanding electronic structure analyses. Here we introduce the penetration index, a purely geometrical, size-normalized descriptor derived from atomic positions and covalent/van der Waals radii, which is related to covalency. For a broad set of systems, including diatomic molecules and ions, phosphine chalcogenides, hydrogen- and halogen-bonded complexes, and halonium ions, the penetration index shows remarkably strong correlations (R2 up to 0.99) with established computational covalency descriptors such as ΔESC in bonded-ALMO-EDA, VXC in IQA, ΔECT in ALMO-EDA, DDEC6 bond orders, and 3c–4e bonding percentages. In all cases, it outperforms bare interatomic distances, transforming scattered trends into linear relationships. The penetration index thus offers a robust, low-cost, and transferable structural metric that correlates with covalency-related bonding terms for both covalent and noncovalent interactions. Access copy available to the general public Unrestricted info:eu-repo/semantics/openAccess by-nc https://creativecommons.org/licenses/by-nc/4.0/deed.es info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Gonzalo, Jorge Merino, Pedro Universidad de Zaragoza (orcid)0000-0002-2202-3460 Echeverría, Jorge 2013 765 Universidad de Zaragoza Dpto. Química Orgánica Área Química Orgánica (2026), [8 pp.] Dalton Trans. Dalton Transactions 1477-9226 1381899 http://zaguan.unizar.es/record/169339/files/texto_completo.pdf Versión publicada 2743742 http://zaguan.unizar.es/record/169339/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:169339 articulos driver 2026-02-24-14:47:02 ARTICLE