Structures of protonated benzene dimer and intermolecular interaction decomposition via symmetry-adapted perturbation theory

► Parallel-displaced, T-shaped, and canted structures of protonated benzene dimer are found using CCSD(T)/aug-cc-pVTZ. ► Interaction energies are −11.4, −10.7, and −10.0 kcal mol−1 for parallel-displaced, T-shaped, and canted structures. ► The electrostatic interaction energy is maximal when the protonation site is directed toward the top face of benzene. ► The dispersion interaction energy is maximal for the parallel-displaced structure by 2.0 kcal mol−1. ► Induction accounts for ∼25% of the benzene-benzenium interaction and is independent of orientation.