We trained a D-MPNN and FFNN on 80-10-10 random splits of 28,772 vertical excitation energies from our full set of vacuum TD-DFT calculations. This model achieved a test MAE of 0.12 eV (14.99 nm), and the predictions are shown in Figure . This model became the auxiliary model used in the ChempropMultiFidelity approach for the remainder of this work.