Notes on the S22 Set

(All solids - Periodic Table - Home - PM7 Accuracy - Manual - S66 notes)

For a long time semiempirical calculation of intermolecular interactions has been of very low accuracy, however in recent years several attempts have been made to reduce the error by making post-SCF corrections.  This has resulted in several new methods such as PM6-DH2, PM6-DH+, PM6-DH2X, etc.  These methods explored ideas of how to model non-covalent interactions. 

During the development of PM7, the ideas and concepts developed by Hobza, Rezác and Korth were very useful in defining the post SCF correction .  Indeed, prior to their work, developments in this area had almost come to a halt.  These researchers are acknowledged for their generous contributions to the MOPAC project.

Experimental reference data on non-covalent interactions is limited, so extensive use has been made of high-level theoretical results, see: Jurecka, P.; Sponer, J.; Cerny, J.; Hobza, P. Benchmark Database of Accurate (MP2 and CCSD(T) Complete Basis Set Limit) Interaction Energies of Small Model Complexes, DNA Base Pairs, and Amino Acid Pairs. Phys. Chem. Chem. Phys. 2006, 8, 1985–1993. Data