Kinetic Energies Calculated from Density Gradient Expansion

8 Kinetic Energies Calculated from Density Gradient Expansion 

T% being the lowest-order gradient correction to the Thomas-Fermi value. Hence we have from equations (77) and (79) that 

Wang et al.s0 have calculated T0, T2, and Tt using good wave-mechanical densities for closed-shell atoms and a selection of their results is recorded in Table 5. The inequality (80) is seen to be fulfilled. Furthermore, since the Thomas-Fermi statistical theory becomes correct for sufficiently large numbers of electrons, it follows that the importance of T% diminishes continually for heavier atoms. 

We shall comment later on the analogue of the above gradient expansion of the kinetic energy for the exchange plus correlation energy. 

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