Electronic structure via potential functional approximations
  The universal functional of Hohenberg-Kohn is given as a coupling-constant integral over the density as a functional of the potential. Conditions are derived under which potential-functional approximations are variational. Construction via this method and imposition of these conditions are shown to greatly improve the accuracy of the non-interacting kinetic energy needed for orbital-free Kohn-Sham calculations. 
Attila Cangi, Donghyung Lee, Peter Elliott, Kieron Burke, E.K.U. Gross
cond-mat.other