  Electron dispersion forces play a crucial role in determining the structure
and properties of biomolecules, molecular crystals and many other systems.
However, an accurate description of dispersion is highly challenging, with the
most widely used electronic structure technique, density functional theory
(DFT), failing to describe them with standard approximations. Therefore,
applications of DFT to systems where dispersion is important have traditionally
been of questionable accuracy. However, the last decade has seen a surge of
enthusiasm in the DFT community to tackle this problem and in so-doing to
extend the applicability of DFT-based methods. Here we discuss, classify, and
evaluate some of the promising schemes to emerge in recent years. A brief
perspective on the outstanding issues that remain to be resolved and some
directions for future research are also provided.
