Achieving High-Accuracy Intermolecular Interactions by Combining Coulomb-Attenuated Second-Order Møller-Plesset Perturbation Theory with Coupled Kohn-Sham Dispersion.

The dispersion-corrected second-order Møller-Plesset perturbation theory (MP2C) approach accurately describes intermolecular interactions in many systems. MP2C, however, expends much computational effort to compute the long-range correlation with MP2, only to discard and replace those contributions with a simpler long-range dispersion correction based on intermolecular perturbation theory. Here, we demonstrate that one can avoid calculating the long-range MP2 correlation by attenuating the Coulomb operator, allowing the dispersion correction to handle the long-range interactions inexpensively. With relatively modest Coulomb attenuation, one obtains results that are very similar to those from conventional MP2C. With more aggressive attenuation, one can remove just enough short-range repulsive exchange-dispersion interactions to compensate for finite basis set errors. Doing so makes it possible to approach complete basis set limit quality results with only an aug-cc-pVTZ basis, resulting in substantial computational savings. Further computational savings could be achieved by reformulating the MP2C algorithm to exploit the increased sparsity of the two-electron integrals.