Accurate transferable polarization model derived from the monomer electron density

Abstract

Force field have for decades proven to be an indispensable tool for molecular simulations which are out of reach for ab-initio methods. Recent efforts to improve the accuracy of these simulations have focused on the inclusion of many-body interactions in force fields. In this regard, we propose a transferable inducible dipole model which requires only the monomer electron density as input, without the need for atom type specific parameters. Slater dipoles are introduced, the widths of which are derived from the ab-initio monomer density. An additional exchange-repulsion interaction is introduced in our model, originating from the overlap of the delocalized dipoles with other dipoles and the ground state electron density. This interaction has previously been neglected in point dipole models, as the lack of spatial extent of the dipoles prevents the inclusion of an overlap term. The inclusion of this interaction is shown to significantly improve the prediction of three-body energies. Our model is incorporated in a previously proposed non-covalent force field and is benchmarked on interaction energies of dimers contained in the hsg and hbc6 datasets. Furthermore, we demonstrate the transferability of our model to the condensed phase of water, and to the interaction of CO$_2$ and H$_2$O molecules with the ZIF-8 metal-organic framework. The inherent transferability of our model makes it widely applicable to systems like the aforementioned metal-organic frameworks, where no specifically fitted parameters for polarization models are available in the literature.