  The recent non-local correlation functional of Vydrov and van Voorhis[J.
Chem. Phys. 133, 244103 (2010)] is investigated and two new versions of the
functional are suggested as being appropriate for describing van der Waals
interactions in solids. A refitting of the original functional is demonstrated
to result in very accurate interlayer binding energies for weakly bonded
layered solids. A VV10 functional based on the generalized gradient
approximation by Armiento and Mattsson[Phys. Rev. B 72, 085108 (2005)], while
performing slightly worse for interlayer binding is highly successful in
describing the equilibrium geometries of both weakly bonded and close packed
solids.
