  The past few years has brought renewed focus on the physics behind the class
of materials characterized by long-range interactions and wide regions of low
electron density, sparse matter. There is now much work on developing the
appropriate algorithms and codes able to correctly describe this class of
materials within a parameter-free quantum physical description. In particular,
van der Waals (vdW) forces play a major role in building up material cohesion
in sparse matter. This work presents an application to the vanadium pentoxide
(V2O5) bulk structure of two versions of the vdW-DF method, a first-principles
procedure for the inclusion of vdW interactions in the context of density
functional theory (DFT). In addition to showing improvement compared to
traditional semilocal calculations of DFT, we discuss the choice of various
exchange functionals and point out issues that may arise when treating systems
with large amounts of vacuum.
