Geometries and Energies in the Wiggle150 Set. We first investigated the geometries produced by our metadynamics-based workflow. We compared the variation in internal coordinates in our conformer set ("Wiggle150") to that in the large Folmsbee-Hutchison conformer set ("Folmsbee"), in each case comparing the internal coordinate in a given molecule to its corresponding value in the lowest-energy conformer (Figure ). While the vast majority of bonds, angles, and dihedrals in the Folmsbee set were almost identical to those in the lowest-energy conformer, the Wiggle150 set showed huge variance: bond lengths varied by up to 0.1 Å from equilibrium, angles varied up to 20º from equilibrium, and many dihedrals covered the entire range of possible values. This structural diversity leads to dramatically more strained structures: while 94% of the Folmsbee set is within 5 kcal/mol of the ground state, the average Wiggle150 conformer is 103 kcal/mol above the ground state. Overall, the metadynamics-based approach used here led to much greater structural diversity than is typically observed in conformer datasets, making this a particularly challenging benchmark. Evaluating Different Methods on Wiggle150. Despite the difficulty of this benchmark set, many high-quality computational methods performed well (Figure , Table ). Numerous methods achieved a MAE under 1 kcal/mol ("chemical accuracy"), including DLPNO-MP2, DSD-PBEP86, and several range-separated-hybrid density functionals.