Non-Covalent Interactions with Dual-Basis Methods: Pairings for Augmented Basis Sets.

Basis set pairings for dual-basis calculations are presented for the aug-cc-pVXZ (X = D, T, Q) series of basis sets. Fidelity with single-basis results is assessed at the second-order Møller-Plesset perturbation theory (MP2) level within the resolution-of-the-identity (RI) approximation, using the S22 set of noncovalent interactions and a series of electron affinities from the G3 set. Root-mean-squared errors for the S22 set are 0.019 kcal mol(-1) or lower, with a maximum deviation of 0.44%, and errors in nuclear structures are 0.09% or lower. Cost savings of 60-93% (RI-MP2 energies) and 50-88% (RI-MP2 gradients) are demonstrated. Spin-component-scaled MP2 [SCS(MI)-MP2] scaling parameters are provided for the aug-cc-pVXZ series, and dual-basis results are shown to be consistent without reoptimization of the single-basis parameters. Explicit handling of linear dependence in the basis set projection scheme is also provided. These dual-basis pairings will be helpful for accelerating accurate Hartree-Fock, density functional theory (DFT), MP2 and scaled MP2, and so-called doubly hybrid DFT calculations of intermolecular interactions (and other systems), where augmented basis sets are physically important.