Since the polarizability is connected to chemical hardness ⌘ in conceptual DFT, which is defined by the HOMO-LUMO gaps, we first examined the GFN2-computed HOMO-LUMO gaps for both the PubChemQC subset and the hexamers from the wide range polarizability set. In principal, the highly polarizable ⇡-conjugated species should have smaller HOMO-LUMO gaps. Unfortunately, there was not a useful correlation between the calculated polarizability and molecular HOMO-LUMO gap (Figure ), likely because GFN2 is not parameterized for HOMO or LUMO eigenvalues to connect with ionization potential or electron a nity.