Analyticity with respect to external potential in DFT and implications for Kohn-Sham computation

All the basic DFT quantities --- density, intrinsic energy, Hartree-exchange-correlation energy,
and energy in excess of ground --- are analytic in the external Kohn-Sham potential
under a gap condition, within the standard Lieb framework. (The latter fixes the function spaces
and norms of interest). I discuss the proof of this result and its significance for Kohn-Sham
computation. It favors iterative strategies that focus on potential rather than, as in the
most-usual methods, on density.