so named because vdW forces (as codified in the eponymous equation of state) involve both long-range attraction (E disp ) and short-range repulsion (E exch ). It can be seen from Fig. that these are the only two energy components that are significant in (benzene) 2 , as both E ind and E elst are relatively small and also relatively flat along the cofacial sliding coordinate that we consider. (The electrostatic energy is as large as |E elst | = 2.5 kcal/mol in the eclipsed-cofacial geometry but the induction energy is truly negligible, |E ind | ≤ 0.2 kcal/mol.) As documented previously using several different energy decomposition analyses (EDAs), including the XSAPT+MBD method that is used here, the vdW surface E vdW exhibits the same conformational preferences as E int . In particular, the eclipsed-cofacial geometry is a saddle point that connects to a slip-stacked local minimum. The molecular physics is that Pauli repulsion forces displacement of the nuclei on one monomer relative to those on the other. Displacement by 1.8 Å relieves enough of the repulsion associated with the nuclear cusps in the electron density while preserving favorable dispersion interactions that are reduced as a function of parallel-displacement. Fig. : XSAPT+MBD interaction potential and energy components for [18]annulene dimer, along a sliding coordinate that is indicated, at a fixed intermolecular separation of 3.2 Å that corresponds to the parallel-displaced minimum-energy structure.