Importance of anisotropy in the evaluation of dispersion interactions

The evaluation of dispersion interaction energies, with the goal of correcting the performance of density functional theory (DFT) methods, is currently a topic of intensive research. Most of the dispersion-corrected DFT methods (DFT-D) rely on an additive correction expression based on the use of isotropic dispersion coefficients. This, however, undermines an important aspect of the interaction, i.e., its anisotropic nature. We demonstrate that, for systems of sufficient size, such as benzene dimers and DNA base pairs, the inclusion of anisotropy, through the use of the Hirshfeld method, results in an increase of dispersion energy values by up to 30%.