  F.E. Harris has been a significant partner in our work on orbital-free
density functional approximations for use in ab initio molecular dynamics. Here
we mention briefly the essential progress on single-point functionals since our
original paper (2006). Then we focus on the advantages and limitations of
generalized gradient approximation (GGA) non-interacting kinetic-energy
functionals. We reconsider the constraints provided by near-origin conditions
in atomic-like systems and their relationship to regularized versus physical
external potentials. Then we seek the best empirical GGA for the
non-interacting KE for a modest-sized set of molecules with a well-defined
near-origin behavior of their densities. The search is motivated by a desire
for insight into GGA limitations and for a target for constraint-based
development.
