(2.2.2) Gould : Kohn-Sham DFT typically means any DFT approximation that employs a set of one-body orbitals, usually denoted {φ i }, to produce a kinetic energy functional, T s [ρ] := T s [{φ i }] that approximates the many-body kinetic energy, T [Ψ] = Ψ|T |Ψ . Generalized Kohn-Sham DFT incorporates traditional approaches to DFT as well as "hybrid" functionals, which allow for nonlocal operator treatment of the Hartree-Fock exchange terms. As a result, one can replace a many-body interacting Hamiltonian, H, by a simpler-to-evaluate one-body Kohn-Sham effective Hamiltonian: