Yang, W; Parr, RG; Lee, C, *Various functionals for the kinetic energy density of an atom or molecule*,
Physical Review A - Atomic, Molecular, and Optical Physics, vol. 34 no. 6
(1986),
pp. 4586-4590 [doi] .
**Abstract:**

*Various approximate density functionals for the kinetic energy density of atoms and molecules are analyzed. These include the results of a gradient expansion to first and second orders and a form recently derived from a new Greens function approximation [W. Yang, preceding paper, Phys. Rev. A 34, 4575 (1986)]. All the approximate functionals studied diverge to minus infinity at a nucleus, due to the 2 term that is in them, while the exact functional is positive and finite everywhere. Away from nuclei, however, the Hartree-Fock results are well reproduced, including the atomic shell structure. New functionals are proposed to correct the divergent behavior, and accurate total kinetic energy values are obtained from a new formula for kinetic energy density tMP(r)=Ck(r)5/3 +(1/72)(r)2/(r)+ (1/12)2(r), with a divergence correction. © 1986 The American Physical Society.*