In our automated workflow, the DFTB calculations are run as follows. A SMILES string corresponding to an arbitrary molecule is internally converted into a set of Cartesian coordinates that are handed to the DFTB+ code as input, along with the selected level of theory. A python script is started to perform the DFTB calculation via the "atomic simulation environment" (ASE) , which allows for software-agnostic electronic structure calculations. The DFTB calculation itself in our case is a geometry optimization with user-controllable convergence criteria. The geometry optimization is necessary since the HOMO-LUMO gap is sensitive to the selected geometry. Ideally, the global minimum energy structure should be identified since it is the molecular conformation likely adopted by the molecule in question. At the end of the calculation, the value of the HOMO-LUMO gap is collected from the output corresponding to the converged molecular structure. There are two shortfalls that may occur in the DFTB calculation step: i) failure to achieve self-consistent-charge convergence of the atomic charges in DFTB density calculations, and ii) failure to achieve a converged minimum energy optimized structure. Our algorithm automatically detects those cases and removes them from the database of molecules.