Abstract
The theoretical description of sparse matter attracts much interest, in particular for those groundstate
properties that can be described by density functional theory (DFT). One proposed approach,
the van der Waals density functional (vdW-DF) method, rests on strong physical foundations and
offers simple yet accurate and robust functionals. A very recent functional within this method called
vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B, in print] stands out in its attempt to use
an exchange energy derived from the same plasmon-based theory from which the nonlocal correlation
energy was derived. Encouraged by its good performance for solids, layered materials, and aromatic
molecules, we apply it to several systems that are characterized by competing interactions. These
include the ferroelectric response in PbTiO3, the adsorption of small molecules within metal-organic
frameworks (MOFs), the graphite/diamond phase transition, and the adsorption of an aromaticmolecule
on the Ag(111) surface. Our results indicate that vdW-DF-cx is overall well suited to
tackle these challenging systems. In addition to being a competitive density functional for sparse
matter, the vdW-DF-cx construction presents a more robust general purpose functional that could
be applied to a range of materials problems with a variety of competing interactions.
