Evaluation of van der Waals density functionals for layered materials

In 2012, Bjorkman et al. posed the question "Are we van der Waals ready?" [T. Bjorkman et al., J. Phys.: Condens. Matter 24, 424218 (2012)] about the ability of ab initio modeling to reproduce van der Waals (vdW) dispersion forces in layered materials. The answer at that time was no, however. Here we report on a new generation of vdW dispersion models and show that one, i.e., the fractionally ionic atom theory with many-body dispersions, offers close to quantitative predictions for layered structures. Furthermore, it does so from a qualitatively correct picture of dispersion forces. Other methods, such as D3 and optB88vdW, also work well, albeit with some exceptions. We thus argue that we are nearly vdW ready and that some modern dispersion methods are accurate enough to be used for nanomaterial prediction, albeit with some caution required.