Another potential source of error is the choice of modified Seminario method for derivation of bond and angle force constants. However, this method has been shown to accurately reproduce QM vibrational frequencies, and importantly also reproduce QM intramolecular potential energy surfaces of drug-like molecules when combined with the QUBE non-bonded and torsion parameters. There are also additional considerations involved in using a library of torsional parameters alongside system-specific non-bonded parameters. The torsional parameters are fit using one set of non-bonded parameters but are then used for a range of environment-dependent nonbonded terms. This is likely the reason for the importance of regularizations in this study.