Comparing Symmetry-Adapted Perturbation Theory to Intermolecular Energy Decomposition Analysis Based on Absolutely Localized Molecular Orbitals

Energy decomposition analysis (EDA) can provide insight into noncovalent interactions, even though the individual energy components (electrostatics, Pauli repulsion, polarization, dispersion, etc.) are not uniquely defined within quantum mechanics. The present work examines the two titular EDA schemes and elucidates the degree of transferability between their components. We first demonstrate that a many-body dispersion (MBD) model can replace the conventional definition of dispersion in symmetry-adapted perturbation theory (SAPT), preserving reasonable accuracy as compared to third-order SAPT but reducing the computational cost to be comparable to density functional theory (DFT). Individual SAPT + MBD energy components exhibit good correlation with those computed using the absolutely localized molecular orbital (ALMO) EDA scheme, which is built around DFT, such that qualitative explanations and chemical trends are likely to be similar in either approach. SAPT + MBD and ALMO-EDA electrostatic energies are nearly identical, provided that a SAPT-style direct-product reference state is used for ALMO-EDA, but other energy components exhibit substantial quantitative differences. These conclusions hold across a range of density functionals used in the ALMO-EDA calculations, and for different choices of the “dispersion-free” functional that is used to isolate the dispersion energy from the target functional’s interaction energy. The present work provides calibration plots to translate between SAPT + MBD and ALMO-EDA energy components. For a large data set of dimers representing ligand–protein interactions, SAPT + MBD calculations afford superior agreement with the best ab initio benchmarks, as compared to calculations using the state-of-the-art ωB97M-V functional, especially when triple-ζ basis sets are used for SAPT. This conclusion holds even when three-body (Axilrod–Teller–Muto) dispersion corrections are added to the ωB97M-V results.