SELF-CONSISTENT APPROXIMATION TO THE KOHN-SHAM EXCHANGE POTENTIAL

A scheme of approximation of the Kohn-Sham exchange potential vx is proposed, making use of a partitioning of vx into the long-range Slater vS and the short-range response vresp components. A model potential vrespmod has been derived from dimensional arguments. It possesses the proper short-range behavior and the atomic-shell stepped structure characteristic for vresp. When combined with the accurate vS, vrespmod provides an excellent approximation to the exchange potential of the optimized potential model vxOPM. With the generalized-gradient approximation to vS vrespmod provides an efficient density-functional-theory approach that fits closely the form of the accurate exchange potential and yields reasonably accurate exchange and total energies as well as the energy of the highest occupied orbital. © 1995 The American Physical Society.