A completely new nonlocal exchange-energy functional in terms of a $P_4$,3(x) Padé approximant is derived from its kinetic-energy-functional counterpart. The new formula exhibits correct asymptotic behavior for large and small density gradients. It can be written in the form of an exchange functional recently proposed by Becke. Furthermore, our exchange functional yields very good exchange energies when evaluated with Hartree-Fock–quality densities. Its functional derivative does not diverge for atomic systems, allowing one to obtain fairly good variational densities and exchange energies.

• Received 1 March 1988

DOI:https://doi.org/10.1103/PhysRevA.38.1697