Spatially Homogeneous QM/MM for Systems of Interacting Molecules with on-the-Fly ab Initio Force-Field Parametrization

Quantum and classical mechanics are combined in a hybrid many-body interaction model to enable the computationally affordable study of systems containing many interacting molecules. This model treats intramolecular and pairwise intermolecular interactions quantum mechanically, while many-body electrostatic induction effects are approximated using a polarizable force field. In this paper, we demonstrate that parametrizing the force field with distributed multipoles and atom-centered polarizabilities obtained on-the-fly from ab initio quantum mechanical monomer calculations makes the model very accurate and eliminates nearly all empiricism. Test calculations on water, formamide. hydrogen fluoride, and glycine-water clusters, all of which exhibit strong many-body interactions, are presented. The performance of the hybrid model is competitive with related point-charge embedding models.