  We present a perturbative approach within the scope of Kohn-Sham density
functional theory (DFT). The method is based on the exact exchange-only
optimized effective potential method, and correlation is included via
perturbation expansion using Rayleigh-Schrodinger (RS) perturbation theory
(PT). The correlation potential is constructed from Moller-Plesset formulation
of RS calculations. This naturally leads to a new iterative scheme when finite
order perturbation theory is employed. The new iterative procedure can be taken
as a self-consistent parameter-free DFT PT, and, as such, provides correlation
energy which is explicitly functional of the self-consistent orbitals,
eigenvalues and also of the exchange-correlation potential.
