As an aside, we note that the B3LYP energies (and gradients) in the dataset do not account for long-range non-covalent interactions. Given the size of this molecule these could be significant, as stressed recently for model "toy" carbon chains, and, as noted above, by adding a classical many-body (for 5 and higher-bodies) polarization term for ab initio energies, by Paesani and co-workers for small hydrocarbons. Future work could include augmenting the present energies by long-range interactions.