The parameterization approach used to determine bond and angle harmonic force constants in traditional force fields, such as OPLS and AMBER, is to fit them to reproduce QM data or experimental normal mode frequencies. This creates interdependencies in the force field parameters. That is, bond and angle parameters depend on the non-bonded and torsional parameters used during the fitting process, and therefore they cannot be easily transferred to the QUBE force field. Instead, we derive bond and angle force constants directly from the QM Hessian matrix of the molecule under study, while equilibrium bond lengths and angles are taken from the optimized geometry of the molecule. This method is a modification of the Seminario method, and is based on the computation of the eigenvalues and eigenvectors of the partial Hessian matrix, k AB :