Tests of nonlocal kinetic energy functionals

The accuracies of various nonlocal kinetic energy functionals are evaluated by considering the kinetic energies of rare gas atoms and the kinetic energy contributions to the interaction energy (ΔEk) for pairs of rare gas atoms. The most accurate kinetic energy functionals are those that combine the density gradient factors of accurate exchange energy functionals with the Thomas–Fermi (TF) kinetic energy functional; these functionals, including a new one proposed in this paper, give total atomic kinetic energies to within 1%, as well as accurate values of ΔEk. Other gradient-corrected functionals give good results for total kinetic energies, but give poor results for ΔEk.