Padé approximants in density functional theory

Padé approximants are used to represent the total correlation functional Ecγ[ϱ] and its kinetic-energy component Tcγ[ϱ], where the parameter γ is the electron-electron interaction coupling contstant within the adiabatic connection formalism. The exact relations between Ecγ[ϱ] are emploed to generate the associated Tcγ[ϱ] functional from its parent Ecγ[ϱ] functional. Numerical results (with γ = 1) on the first 18 neutral atoms confirm the soundness of this procedure. It is proved that no local representations of these functionals can be exact for the nonuniform electron gas. However, it is still useful to design local functionals that are as accurate as possible.