POLYNOMIAL AND PADE REPRESENTATIONS FOR THE KINETIC COMPONENT T-C[RHO] OF THE CORRELATION-ENERGY DENSITY-FUNCTIONAL

Polynomial and Fade representations of the kinetic energy component T- c[rho] of the correlation energy density functional E-c[rho] are prese nted in this article. Two approximate local formulas similar to the Wi gner form for E-c[rho] are investigated for T-c[rho]. Applications of these formulas along with their two polynomial counterparts are carrie d out for atoms, ions, and a few simple molecules. Numerical predictio ns of T-c values are made for these species. Both Hartree-Fock and sel f-consistent-field densities are used in their evaluations. Recommende d at this time is the two-parameter Pade [0, 1] formula T-c[rho] = int egral a(0)rho/(1 + b(0) rho(-1/3)) dr, with a(0) = 0.1658 and b(0) = 6 .102 (atomic units). (C) 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 513-522, 1998.