Predicting C-H/π interactions with nonlocal density functional theory

We examine the performance of a recently developed nonlocal density functional in predicting a model noncovalent interaction, namely the weak bond between an aromatic π system and an aliphatic C-H group. The new functional is a significant improvement over traditional density functionals, providing results which compare favorably to high-level quantum-chemistry techniques, but at considerably lower computational cost. Interaction energies in several model C-H/π systems are in good general agreement with coupled-duster calculations, though equilibrium distances are consistently overpredicted when using the revPBE functional for exchange. The new functional predicts changes in energy upon addition of halogen substituents correctly.