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.