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<p>Intermolecular interactions are critical to many chemical phenomena, but their accurate computation using
<i>ab initio</i> methods is often limited by computational cost. The recent emergence of machine learning (ML)
potentials may be a promising alternative. Useful ML models should not only estimate accurate interaction
energies, but also predict smooth and asymptotically correct potential energy surfaces. However, existing
ML models are not guaranteed to obey these constraints. Indeed, systemic deficiencies are apparent in the
predictions of our previous hydrogen-bond model as well as the popular ANI-1X model, which we attribute
to the use of an atomic energy partition. As a solution, we propose an alternative atomic-pairwise framework
specifically for intermolecular ML potentials, and we introduce AP-Net—a neural network model for interaction energies. The AP-Net model is developed using this physically motivated atomic-pairwise paradigm and
also exploits the interpretability of symmetry adapted perturbation theory (SAPT). We show that in contrast to other models, AP-Net produces smooth, physically meaningful intermolecular potentials exhibiting
correct asymptotic behavior. Initially trained on only a limited number of mostly hydrogen-bonded dimers,
AP-Net makes accurate predictions across the chemically diverse S66x8 dataset, demonstrating significant
transferability. On a test set including experimental hydrogen-bonded dimers, AP-Net predicts total interaction energies with a mean absolute error of 0.37 kcal mol−1, reducing errors by a factor of 2-5 across
SAPT components from previous neural network potentials. The pairwise interaction energies of the model
are physically interpretable, and an investigation of predicted electrostatic energies suggests that the model
‘learns’ the physics of hydrogen-bonded interactions.
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