The geometric component of the objective function is computed from the deviations of bond-lengths, bondangles and improper torsions, in structures optimized with the force field, from their values in corresponding structures optimized with QM (Section 2.1.4). As shown in Figure , the fitting process led to improved overall agreement between force field and QM geometries; compare the initial (red) and final (green) histograms. The portion of the blue histogram on the negative / positive x-axis shows the percentage of targets where accuracy is improved / degraded, respectively. The accuracy was somewhat reduced for a small minority of conformers, as evident from the histogram of differences (blue), but this is as expected, because compromises have to be made for some molecules in order to improve the accuracy for others that use the same parameters. Table provides a physically interpretable perspective of these results, showing that the RMS errors of bond-lengths, bond-angles, and improper torsions, in the optimized geometries, decreased by 14-49% with training.