CHAPTER 8: Dispersion Energies via Division Into Atoms or Larger Units

Here we consider the description of dispersion (van der Waals) interactions via conceptual division of the interacting objects into atoms or larger units. While early methods in this category (e.g. a pairwise sum of Lennard-Jones potentials) have somewhat limited applicability, there are modern approaches that start from semi-local density functional theory and add numerically-efficient atom-based corrections, with considerable success. We describe some of these recent state-of-the-art approaches in some detail, as well as noting some remaining difficulties for highly polarisable and low-dimensional systems.