Interaction energies were computed using XSAPT+MBD. Recent overviews and illustrative examples of this methodology can be found elsewhere. Briefly, XSAPT+MBD is a hybrid model in which the dispersion and exchange-dispersion terms of conventional second-order SAPT are replaced with a modified version of the MBD model developed by Tkatchenko and coworkers. A charge-embedding scheme is also employed, 32 based on Charge Model 5 for the atomic charges, although for the nonpolar monomers that are considered here, the induction energies are small and the charge embedding changes the interaction energies only by ∼ 0.5 kcal/mol (see Table ). All together, the result is a decomposition of the total intermolecular interaction energy (E int ) into physically meaningful components: 12