Levels of symmetry-adapted perturbation theory (SAPT). II. Convergence of interaction energy components.

Abstract

Symmetry-adapted perturbation theory (SAPT) is a valuable theoretical technique useful in quantifying intermolecular interaction energies in terms of four physically meaningful components: electrostatics, exchange-repulsion, induction/polarization, and London dispersion. We present a systematic analysis of the convergence of SAPT total and component energies with respect to the level of theory and basis set using an extended database of 4569 van der Waals dimer geometries. Our analysis supports the use of SAPT0/aug-cc-pVDZ over previously recommended sSAPT0/jun-cc-pVDZ as an economical level of SAPT. Our previous recommendations of SAPT2+/aug-cc-pVDZ and SAPT2+(3)δMP2/aug-cc-pVTZ as medium and high cost variants, respectively, remain unchanged. However, SAPT0/aug-cc-pVDZ and SAPT2+/aug-cc-pVDZ total interaction energies on average rely on error cancellations, so they should be used with caution when parameterizing SAPT-based force fields and intermolecular potentials. SAPT2+(3)/aug-cc-pVTZ shows quantitatively accurate component energies, making it the preferred choice for applications when feasible. Finally, we examine a focal point approximation that approaches the accuracy of SAPT2+(3)δMP2/aug-cc-pVTZ with a significantly reduced cost.