Benchmarking of the R Anisotropic Dispersion Energy Term on the S22 Dimer Test Set.

The effects of including the anisotropic E term to the dispersion energy in addition to the leading E term are examined by using the effective fragment potential (EFP) method on the S22 test set. In this study, the full anisotropic E term is computed whereas the isotropic and spherical approximations are used for the E term. It is found that the E term is positive for hydrogen-bonded complexes and has a magnitude that can be as large as 50% of E, giving rise to larger intermolecular distances than those obtained with E alone.