Application of an empirical dispersion potential to van der Waals binding in nitromethane, pentaerythritol, and pentaerythritol tetranitrate

The Grimme potential is used to represent van der Waals interactions in molecular crystals.Agreement with experiment for equilibrium volumes is shown to be at the level of a few percent.From the results presented, it is evident that there is a competition between improving the (Gaussian) basis set, which increases the equilibrium volume, and improved exchange-correlation potential which decreases it. Therefore, for accurate ab initio studies of van der Waals bonded molecular crystals, it is important to use both good quality basis sets and exchange-correlation potentials capable of describing the van der Waals interaction.