On the performance of the semiempirical quantum mechanical PM6 and PM7 methods for noncovalent interactions

In this Letter, we compare the recently released semiempirical method PM7 with its predecessor, PM6 with post-SCF corrections. These corrections were introduced in order to improve the description of noncovalent interactions (dispersion, hydrogen bonds and halogen bonds) and have become an integral part of PM7. A large collection of data on noncovalent interactions, covering not only interaction energies but also conformational changes and geometries, is used as a benchmark. Among the methods tested, PM6 with the latest corrections (PM6-D3H4X) yields the best results. PM7 yields only slightly worse results but brings additional improvements in the description of other molecular properties.