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.