  The van der Waals density functional (vdW-DF) of Dion et al. [Phys. Rev.
Lett. 92, 246401 (2004)] is a promising approach for including dispersion in
approximate density functional theory exchange-correlation functionals. Indeed,
an improved description of systems held by dispersion forces has been
demonstrated in the literature. However, despite many applications, standard
general tests on a broad range of materials are lacking. Here we calculate the
lattice constants, bulk moduli, and atomization energies for a range of solids
using the original vdW-DF and several of its offspring. We find that the
original vdW-DF overestimates lattice constants in a similar manner to how it
overestimates binding distances for gas phase dimers. However, some of the
modified vdW functionals lead to average errors which are similar to those of
PBE or better. Likewise, atomization energies that are slightly better than
from PBE are obtained from the modified vdW-DFs. Although the tests reported
here are for "hard" solids, not normally materials for which dispersion forces
are thought to be important, we find a systematic improvement in cohesive
properties for the alkali metals and alkali halides when non-local correlations
are accounted for.
