Ten known EMs, all with experimentally determined crystal structures, were chosen for validation of CSP methods. The test set of EMs studied is shown in Figure . Some of the validation molecules are known to exhibit polymorphism; the number of known polymorphs for each molecule is shown in parentheses in Figure . CSP was performed using the Global Lattice Energy Explorer (GLEE) package, which uses a low-discrepancy, quasi-random sampling of crystal packing variables to explore the lattice energy surface, followed by rigid-molecule lattice energy minimization using an intermolecular force field (described below). Molecular geometries of each molecule were optimized using DFT (PBE0/aug-cc-pVDZ, using Gaussian 36 ) starting from the conformations in their observed crystal structures. The test set contains mostly rigid molecules, so a rigidmolecule approach was taken for generating predicted crystal structures using the gas phase optimized minimum of each EM. Low energy predicted crystal structures were re-optimized using solid state DFT to account for molecular distortion due to intermolecular interactions in the crystal structures. We analyze the impact of DFT re-optimization on the quality of the predictions.