Non-covalent interactions between molecular dimers (S66) in electric fields
We present a systematic study of interaction induced dipole electric properties of all molecular dimers in the S66 set, relying on CCSD(T)-F12b/aug-cc-pVDZ-F12 as reference level of theory. For field strengths up to $\approx$5 GV m$^{-1}$ the interaction induced electric response beyond second order is found to be insignificant. Large interaction dipole moments (i.e. dipole moment changes due to van der Waals binding) are observed in the case of hydrogen bonding oriented along the intermolecular axis, and mostly small interaction dipole moments are found in dimers bonded by $π$-stacking or London dispersion. The interaction polarizabilities (i.e. polarizability changes due to van der Waals binding) were generally found to be small but always with a positive-valued principal component approximately aligned with the intermolecular axis, and two other negative-valued components. Energy decompositions according to symmetry adapted perturbation theory (SAPT0/jun-cc-pVDZ) suggest that electrostatics dominates the interaction dipole moment. First-order SAPT0 decompositions into monomer-resolved contributions establish a quantitative link between electric properties of monomers and dimers. Using the aug-cc-pVQZ basis and non-empirical PBE semilocal exchange-correlation kernels, we also assess how density functional approximations in the nonlocal exchange and correlation parts affect the predictive accuracy: While dRPA@PBE0 based predictions are in excellent overall agreement with coupled cluster results, the computationally more affordable LC-$ω$PBE0-D3 level of theory also yields reliable results with relative errors below 5\%. PBE alone, even when dispersion corrected, produces larger errors in interaction dipole moments and polarizabilities.