  Quantum transport through single molecules is very sensitive to the strength
of the molecule-electrode contact. When a molecular junction weakly coupled to
external electrodes, charging effects do play an important role (Coulomb
blockade regime). In this regime, the non-equilibrium Green function is usually
substituted with master equation approaches, which prevents the density
functional theory from describing Coulomb blockade in non-equilibrium case.
Last year, we proposed an Ansatz to combine the non-equilibrium Green function
technique with the equation of motion method. With help of it, Coulomb blockade
was obtained by non-equilibrium Green function, and completely agrees with the
master equation results [Phys. Rev. B \textbf{76}, 045408 (2007)]. Here, by the
Ansatz, we show a new way to introduce Coulomb blockade correction to DFT
calculation in non-equilibrium case. And the characteristics of Coulomb
blockade are obtained in the calculation of a $toy$ molecule correctly.
