We evaluated E min for molecules in the QM9 dataset, a popular dataset for computational chemistry studies, comprised of 134,000 molecules with up to 9 heavy atoms (i.e., C, O, N, F) from the larger GDB-17 dataset. The molecules in QM9 are found by enumerating the complete list of graphs for molecules up to 9 heavy atoms before using heuristics to remove nonphysical molecules. E min was calculated by first grouping QM9 molecules by their molecular formulas. Among grouped molecules from each molecular formula, the lowest enthalpy constitutional isomer was identified as the reference (i.e. min([E j ∀j = 1, 2, ..., n])) for calculating E min . E min is 0 for the reference molecule while all other isomers have positive E min values.