The exact E elst calculation in Fig. uses SAPT electrostatics, computed at the LRC-ω GDD PBE/def2-TZVPD level in order to be consistent with XSAPT + MBD calculations to follow, while the quadrupolar calculation uses the quadrupole tensor Θ for C 6 H 6 that is obtained at the same level of theory. Consistent with organic chemistry lore, quadrupole-quadrupole repulsion in the face-to-face orientation would push the system away from the sandwich geometry and into an offset-stacked arrangement [Fig. ], while quadrupolar attraction in the perpendicular orientation favors a T-shaped geometry over an L-shaped one [Fig. 28(d)]. However, these results are inconsistent with exact electrostatics calculations. For the faceto-face arrangement, contours of (exact) E elst are relatively flat along the lateral displacement coordinate, [Fig. 28(b)], at least for typical π-stacking distances, indicating that electrostatics is largely ambivalent towards offset-stacking. This is emphasized in Fig. ), which plots one-dimensional slices at the minimumenergy stacking distance, R = 3.4 Å. If anything, exact electrostatics favors the sandwich configuration rather than the offset-stacked geometry, albeit very weakly. Meanwhile, in the edge-to-face geometry, exact electrostatics favors an L-shaped geometry with a 1 Å offset, which is seldom observed, 240 rather than a T-shaped geometry with no offset.