Figure . Molecule pairs from the Individually Different SMIRNOFF set display visual geometric differences. The displayed molecules were identified from the set using the descriptor method in Section 3.1. For each molecule, shown in a 2D inset, we visualize the minimized conformer with SMIRNOFF (darker colors) and GAFF -representing all non-SMIRNOFF force fields (lighter colors). ( ) SMIRNOFF predicts the acylcyanide group to be near perpendicular to the aromatic ring, while GAFF makes it near planar. The two force fields disagree on the appropriate torsion angle for the C-N=N-C bond in the azo group. (3) Again, the SMIRNOFF and GAFF force fields disagree on the planarity of the azo group where the orientation of the aldehyde group agrees between the two force fields. ( ) The substituted hydrazone's change in planarity dominates this molecule with the hydrazone descriptor. In this molecule with a thiocarbonyl, GAFF keeps all carbons planar while SMIRNOFF allow the carbon-carbon single bonds to rotate. This molecule pairs thiocarboxylic acid amide and primary amine descriptors where GAFF predicts the primary amine to bend out of plane, while SMIRNOFF predicts all heavy atoms to be planar.