There is no new information here, beyond what is contained in ∆ρ elec (r) and ∆ρ hole (r). Since the latter quantities have names that invoke both their physical meaning and their connection to the particle/hole formalism of TD-DFT, we will use ∆ρ elec (r) and ∆ρ hole (r) rather than ∆ρ + (r) and ∆ρ -(r). Ciofini et al. introduced what is now a widely-used measure of charge separation, which they call D CT and which is equal to the distance between the centroids of ∆ρ elec (r) and ∆ρ hole (r). However, this quantity is precisely equivalent to d - e-h as defined in Eq. (5.13). A more detailed definition, for both d - e-h and d + e-h , is