Direct Evaluation of Nonbonding Interactions from ab Initio Calculations

Nonbonding interatomic interactions underlie a variety of biological events, including ligand binding to proteins and molecular assembly. The rigorous characterization of these interactions is necessary if we are, ultimately, to achieve an understanding of these events in terms of intermolecular forces. Here, we show how fitting of particular second derivatives extracts direct information on atom-atom nonbonding interactions. We present a novel technique based on these derivatives for extracting such properties as atomic partial charge, transferability, anisotropy of atom-atom repulsion and polarizability, as well as the constants that characterize these interactions, from the quantum mechanical energy surfaces.