Self-consistent approximation to the Kohn-Sham exchange potential

A scheme of approximation of the Kohn-Sham exchange potential vₗ is proposed, making use of a partitioning of vₗ into the long-range Slater vₒ and the short-range response vₑ₄ₒ₏ components. A model potential vₑ₄ₒ₏^mod has been derived from dimensional arguments. It possesses the proper short-range behavior and the atomic-shell stepped structure characteristic for vₑ₄ₒ₏. When combined with the accurate vₒ, vₑ₄ₒ₏^mod provides an excellent approximation to the exchange potential of the optimized potential model vₗ^OPM. With the generalized-gradient approximation to vₒ vₑ₄ₒ₏^mod 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.