Four iterative methods were used to solve the schrödinger equation on a rectangular scattering region with a uniform potential, namely GMRES, restarted GMRES, BiCGStab and IDR(s). A preconditioner like a shifted-Laplacian is tried to improve the convergence behaviour of GMRES. Finally, a disorded potential is introduced in the form of a random diagonal matrix to see the effects of disorder on the convergence behaviour of the iterative methods.