Differential equation for ground-state electron density of He-like ions for large atomic number

An explicit differential equation satisfied by the ground-state electron de nsity of He-like ions is constructed for large atomic number Z, As in the a uthors' earlier work on the Hookean atom, the result is a linear third-orde r homogeneous differential equation. The first-order interacting density ma trix is then written in terms of the ground-state electron density. A funct ional for the correlation kinetic energy is thereby exhibited in the large Z Limit for these two-electron ions. (C) 1999 Elsevier Science B.V. All rig hts reserved.