Attenuated second-order Moeller-Plesset perturbation theory: performance within the aug-cc-pVTZ basis

Attenuated second-order Moeller-Plesset perturbation theory (MP2) within the finite aug-cc-pVTZ (aTZ) basis set is developed for inter- and intra-molecular non-bonded interactions. A single attenuation parameter is optimized on the S66 database of 66 intermolecular interactions, leading to a very large RMS error reduction by a factor of greater than 5 relative to standard MP2/aTZ. Attenuation introduces an error of opposite sign to basis set superposition error (BSSE) and overestimation of dispersion interactions in finite basis MP2. A variety of tests including the S22 set, conformer energies of peptides, alkanes, sugars, sulfate-water clusters, and the coronene dimer establish the transferability of the MP2(terfc, aTZ) model to other inter and intra-molecular interactions. Direct comparisons against attenuation in the smaller aug-cc-pVDZ basis shows that MP2(terfc, aTZ) often significantly outperforms MP2(terfc, aDZ), although at higher computational cost. MP2(terfc, aDZ) and MP2(terfc, aTZ) often out-perform MP2 at the complete basis set limit. Comparison of the two attenuated MP2 models against each other and against attenuation using non-augmented basis sets gives insight into the error cancellation responsible for their remarkable success.