For comparison with the force field-based results, we also summarize the results of periodic DFT re-optimizations of the low energy crystal structures. To generate the DFT-based CSP results, all force field predicted structures within 10 kJ mol -1 of the global energy minimum for each of the ten EMs were re-optimized. For ATZ the energy window was increased to 12 kJ mol -1 as the experimental match was found at 11.46 kJ mol -1 ; ATZ is an outlier in our overall results, which we discuss further below. For HMX, due to the large molecular energy difference between chair and chair-chair conformers, we performed peroidic DFT on the lowest 10 kJ mol -1 for each conformer. FOX-7, HMX and NTO all possess an experimental polymorph with Z' > 1. Thus, to examine where these would occur in energy if CSP had been performed with higher Z', the experimental structures were independently optimized using the force field (FIT with PBE0/aug-cc-pVTZ multipoles) and periodic DFT and their numerical ranking and relative energies, after each stage of optimization, are shown in Table . Note that for these polymorphs, the numerical ranking and relative energies are lower bounds on what they would be if CSP searches had included high Z'.