  We introduce an orbital free electron density functional approximation based
on alchemical perturbation theory. Given convergent perturbations of a suitable
reference system, the accuracy of popular self-consistent Kohn-Sham density
functional estimates of properties of new molecules can be systematically
surpassed---at negligible cost. The associated energy functional is an
approximation to the integrated energy derivative, requiring only perturbed
reference electron densities: No self-consistent field equations are necessary
to estimate energies and electron densities. Electronic ground state properties
considered include covalent bonding potentials, atomic forces, as well as
dipole and quadropole moments.
