OpenFF's choice of B3LYP-D3(BJ)/DZVP closely follows it with an RMSE in relative energies of 0.52 kcal/mol. And, the computational cost of B3LYP-D3(BJ)/DZVP for a single gradient is only half of the best functional, but depending on the type of dataset, geometry optimization or torsion scans, the cost would scale up with the number of steps taken during the calculation. Within a subset of neutral molecules the RMSE in relative energies with B3LYP-D3(BJ)/DZVP is comparable to the most accurate method. And, the larger errors appear to originate from molecules with charges. However, in practice, the distinctions between levels of theory become evident in the high-energy regions, which are typically excluded during force field training with torsion profiles as they are thermally irrelevant. QCFractal+QCEngine. Each entry in the calculation input being sent to the server for computation corresponds to a single molecule and an associated QM calculation schema.