Robust Predictive Power of the Electrostatic Term at Shortened Intermolecular Distances

At distances shorter than equilibrium, electrostatic interactions seem to be a more robust indicator of relative molecular dimer stability than more accurate electronic structure approaches. We arrive at this conclusion by investigating the nonparametric correlation between reference interaction energies at equilibrium geometries (coupled cluster with singles, doubles, and perturbative triples at the complete basis set limit, ΔECCSD(T)CBS,ref) and its various approximate values obtained at a range of distances for a training set of 22 biologically relevant dimers. The reference and other costly methods start to fail to reproduce the equilibrium ranking of dimer stabilities when the intermolecular distance is shortened by more than 0.2 Å, but the full electrostatic component (includes penetration) maintains a high success rate. Such trends provide a new perspective for any applications where inaccurate structures are used out of necessity, such as the scoring of ligands docked to enzyme active sites.