In the conventional DFT implementation, 2 the Kohn-Sham scheme is employed using Kohn-Sham orbitals to bypass the difficulty of approximating the total kinetic energy functional, which is the more difficult energy component to accurately account for. Nevertheless, in principle, DFT does not necessarily require the use of orbitals. In OF-DFT, all energetic contributions are electron density functionals. For example, the total energy, E, of a molecular system is a functional of the ground-state electron density (r), E  E[], and it can be partitioned in the following manner,