This holds for the Hartree energy U [ρ γ ], W λ [ρ γ ] integrand of Eq. 3 in the λ → 0 (exact exchange) and λ → ∞ limit . The scaling of W λ [ρ γ ] in between the two limits is nontrivial and it is known that E XC [ρ] and W λ=1 [ρ] do not scale linearly with γ in general .