AN AB-INITIO CFF93 ALL-ATOM FORCE-FIELD FOR POLYCARBONATES

An all-atom CFF93 force field for polycarbonates based on ab initio ca lculations is reported. Force field parameters are derived by fitting to quantum mechanical total energies, first and second derivatives of total energies, and electrostatic potentials, all generated from ah in itio quantum mechanical calculations on model compounds at HF/6-3 1G level of theory. Valence parameters and ab initio charges are then sca led to correct for differences between experiment and the Hartree-Fock approximation. The van der Waals parameters and the scaling factors f or atomic partial charges are determined from crystal structures. Base d on the force field, molecular mechanics calculations are performed f or several model compounds, and the results are compared with experime ntal values and with the results of the ab initio calculations.