. We make features unitless by multiplying by powers of the Wigner-Seitz radius, r s = 0.62035ρ -1/3 . Fig. shows projection heat maps for six combinations of features for molecular CO, CaO and CrO, all in their lowest energy spin configuration. The features for CO and CaO differ, but in both cases the features are tightly confined to the vicinity of lines. By contrast, CrO has a wider 'spread' in feature space, especially as a function of Hartree-Fock exchange energy densities. This means that CrO is more susceptible to errors in the DFA across a wider region of feature space, meaning that a lack of training data in relevant parts of feature space is likely to lead to errors in the DM21 model.