On the coupling of intermolecular polarization and repulsion through pseudo-potentials

To improve the accuracy and transferability of molecular mechanics force fields, one needs a simple physical description of intermolecular polarization based on quantum chemistry. Ideally, in the quantum-chemical description, each molecule is treated separately and the interactions with other molecules are included as a perturbation. We propose a simple formulation of this perturbation, viz. to model the electrostatic part of the interactions exactly and the repulsive counterpart by a two-parameter pseudo-potential. Tests on three dimers at the Hartree–Fock and MP2 levels show that the interaction energies and the polarized charge densities are well reproduced.