1 ≈ 1 confirms that Γ NTO ≈ d CD1 under these circumstances. However, there are numerous states where λ 2 1 deviates significantly from unity, indicating that two or more principal NTO pairs are qualitatively important. (Note also that λ 1 may exceed unity in full linear response theory; see the discussion surrounding eq. B5.) All of the geometries used to generate Fig. are planar and centrosymmetric (D 2h symmetry), so (∆r