Similar methods may be used to derive the angle force constants, and we introduce a correction to the standard Seminario method which takes into account the geometry of the molecule under study. Consistent improvements in the computed normal modes were demonstrated using this modified Seminario method for a range of molecules. In particular, QM vibrational frequencies for a set of dipeptides were reproduced with an accuracy of 40 cm -1 , which compares favorably with the OPLS force field (47 cm -1 ) and the original Seminario method (104 cm -1 ). Since the derived bond and angle parameters do not depend on the choice of non-bonded and torsion parameters, the derived parameters are suitable for use in the QUBE protein force field. Since large-scale polarization effects are expected to be significantly less important for bond and angle parameters than for charges, we use the library of bonded parameters provided previously (and the same atom types as those used for OPLS-AA/M 1 ).