Charge Transfer Interaction between Ab Initio and Effective Fragment Potential Molecules

(QM) and effective fragment potential (EFP) molecules is derived and implemented. In this QM-EFP method, the charge transfer term is derived by applying second-order perturbation theory; the resulting expression is implemented in GAMESS. The effect of the charge transfer contribution on the accuracy of the total QM-EFP intermolecular interaction energy is evaluated by comparing to the benchmark interaction energies for the S22 and S66 data sets. Charge transfer significantly improves the accuracy of QM-EFP when compared to benchmark values.