Upon careful inspection of the top ranked predicted candidate structures, we found that some of them adopt very similar conformers and packing patterns. These structures correspond to different local minima of the quantum chemical potential energy surface at 0K, but may interconvert at room temperature since the corresponding energy barriers might be comparable to thermal fluctuation. This could be related to disordered structures and has been proposed to be one of the common reasons for the well known over-prediction problem in CSP calculations. To remove this type of non-trivial duplicate from the static landscapes, we clustered similar structures (with RMSD15 better than 1.2 Å) into a single representative structure with the lowest energy among the cluster, similar to what has been done in earlier studies. The rankings of the best matched structures after clustering are shown in Figure (a) (red bars). This improved the rankings, for example, for MK-8876, Target V, and naproxen. Figure 3(b) shows the relative energy between the candidate structure that best matches the experimental structure and the lowest energy predicted structure for each molecule in the subset of molecules with only a single experimentally known crystal structure. The blue and red bars show the results before and after clustering analysis. For most molecules, the known experimental structure corresponds to the lowest energy predicted structure using the r 2 SCAN-D3 functional, thus the relative energy is zero. For a few molecules, the relative energy is less than 0.5 kcal/mol, which is likely within the error bars of the DFT calculations. However, in two systems we observe candidate structures with significantly lower energies (1 kcal/mol) than any experimentally observed polymorph. These two molecules are GSK268499B and MK-8876. Such low energy structures indicate the possibility for stable polymorphs that are yet to be discovered by experiment. A detailed analysis for these molecules will be presented in the following section.