Seamless and Accurate Modeling of Organic Molecular Materials.

The near endless possibilities for assembling molecular materials has long posed a difficult challenge for theory. All crystal-structure prediction methods acknowledge the crucial contribution of van der Waals or dispersion interactions, but few go beyond a pairwise additive description of dispersion, ignoring its many-body nature. Here we use two databases to show how a many-body approach to dispersion can seamlessly model both solid and gas-phase interactions within the coveted "chemical accuracy" benchmark, while the underlying pairwise approach fails for solid-state interactions due to the absence of many-body polarization and energy contributions. Our results show that recently developed methods that treat the truly collective nature of dispersion interactions are able to reach the accuracy required for predicting molecular materials, when coupled with nonempirical density functionals.