The transport and electrostatic equations are mutually connected. The Schrödinger equation depends on the potential energy ϕ(r→) (i.e., on the solution of the Poisson equation), while the Poisson equation depends on the electron and hole concentrations, which can be obtained from the Green’s function of the system (i.e., from the solution of the transport calculation). To perform the simulation, we start from an initial guess potential, we perform the NEGF calculation, and then we solve the Poisson equation with the electron and hole concentrations obtained from the NEGF procedure. The new potential obtained from the Poisson equation is then passed to the NEGF module, and so on recursively until the norm of the difference between the potentials obtained in two successive cycles is less than a given threshold. In our approach, the free charge around each atom is uniformly spread in the cell of the rectilinear grid that contains the atom.