TESTS OF NONLOCAL KINETIC-ENERGY FUNCTIONALS

The accuracies of various nonlocal kinetic energy functionals are eval uated by considering the kinetic energies of rare gas atoms and the ki netic energy contributions to the interaction energy (Delta E(k)) for pairs of rare gas atoms. The most accurate kinetic energy functionals are those that combine the density gradient factors of accurate exchan ge energy functionals with the Thomas-Fermi (TF) kinetic energy functi onal; these functionals, including a new one proposed in this paper, g ive total atomic kinetic energies to within 1%, as well as accurate va lues of Delta E(k). Other gradient-corrected functionals give good res ults for total kinetic energies, but give poor results for Delta E(k).