The use of an empirical dispersion potential to accurately represent the van der Waals interaction in molecular crystals is discussed. Results for nitromethane, pentaerythritol (PE), and pentaerythritol tetranitrate (PETN) are presented for equilibrium volumes using a variety of basis sets ranging in quality in the CRYSTAL program. Agreement with experiment for equilibrium volumes is found to be within a few percent when the Grimme potential and a high-quality basis set is used. (C) 2010 Published by Elsevier B.V.