The key role of electron-nuclear potential energy in determining the ground-state energy of inhomogeneous electron liquids in both real and model atoms

Recent density functional theory (DFT) work of Gl and March (GM) on the groundstate energy E of a two- electron model atom (like He but with inverse square law interparticle repulsion) related E to the electron- nuclear potential energy Uen by E = d1=2_Uen. Also the model of GM satisfies E = 2Uen, but now with harmonic confinement. While modern non- relativistic DFT requires numerical treatment of real atoms, in the exact limit of DFT at large Z, the Thomas- Fermi (TF) theory is regained, where much analytical work can be done. This yields, as Z -> 1, the non- relativistic energy of such neutral atoms as E = d3=7_Uen. The correlated