Nonanalyticity of the optimized effective potential with finite basis   sets
  We show that the finite-basis optimized effective potential (OEP) equations exhibit previously unknown singular behavior.Imposing continuity, we derive new well-behaved finite-basis-set OEP equations that determine OEP for any orbital and any large enough potential basis sets and which adopt an analytic solution via matrix-inversion. 
Nikitas I. Gidopoulos, Nektarios N. Lathiotakis
cond-mat.other physics.chem-ph