Here, numerous forms are available for the enhancement factor F ρ, ∇ρ (see Table in Ref. 5). To date, such GGA KEDFs are still most widely used in applications of sDFT and FDE, in particular the PW91k (also known as LC94) and the revAPBEK functionals (see also Section 5.1 below). The latter has been found to be more accurate than all other available GGA KEDFs in sDFT/FDE calculations in Ref. , and it was found to be superior to PW91k for sDFT simulations of periodic systems by Pavanello and coworkers .