Evaluation of van der Waals density functionals for layered materials

The authors examine a new generation of van der Waals density functionals for the prediction of the geometric and energetic properties of layered materials, and report that the recent inclusion of fractionally ionic effects with many-body dispersions displays outstanding accuracy that almost matches highly accurate ``benchmark'' models, but at a much lower computational cost. Three other methods perform almost as well. They conclude that the evolution of dispersion models is approaching chemical accuracy for van der Waals heterostructures, and that further refinements should seek to improve the underlying polarizability models, such as by including fractional ions or through more accurate treatment of the chemical environment.