This is the aforementioned novel feature. In the adiabatic approximation, this density is independent of time Ḋσ αβ = 0, and is the instantaneous ground state density. It this is matrix which includes an additional contribution to the Fock matrix, without explicit Hartree-Fock exchange (as exchange is included in the XC-functional) to build the Kohn-Sham matrix (informally also known as a Fock matrix):