which gives the usual results for pure states. In the special case of ensembles that preserve fundamental symmetries by equally weighting states related by symmetry operations, 424 one may also rigorously define the Hartree term E FDT H [ρ] and exchange term E FDT x [ρ] using the fluctuation-dissipation theorem. The resulting orbital functionals reduce to their usual definitions in pure states. Hybrid functionals formed on these orbital functionals (e.g., by using