We are now ready to select conformations from the FFreoptimized list for re-optimization by DFT methods and order them into a priority list for re-optimization. Three different approaches were used: pipeline-x; pipeline-ascent and pipelinemix (Figure ). The conformer with the lowest ΔU(FF) from each cluster is prioritized over other conformers. For the first of these, pipelinex, the n_clusters value is chosen as a fraction, x, of the number of conformers. Too small a value for x would group diverse structures together; too large a value would ignore similarities between structures. A good choice of x might lead to a distinct cluster for each unique DFT conformation. Since 85 % of the re-optimized structures in our dataset are unique, we selected a slightly smaller value, 80 % of the total number of conformers, as a good choice for n_clusters (x = 0.8).