Density-gradient expansion of the kinetic-energy functional for molecules

Abstract

The gradient expansion of the molecular kinetic-energy functional is assessed through numerical results for fourteen diatomic and polyatomic molecules. The correlation of the dissociation energies ($D_e$) of molecules with the Weizsacker contribution to the kinetic energy ($T_W$) is established through a plot of $D_e$/$N^2$ against $T_W$ where N is the number of electrons. The conclusions support and extend the observations of Allan, et al. [J. Chem. Phys. 83, 4562 (1985)].