As we shall see in the following sections, none of the above physics-based corrections are guaranteed to make the RDF go exactly to 1 at long r, we thus cannot be certain that the integral in eq. 3 (or in eq. 4) will converge. Therefore, in practice, we must often employ a window function (or 'damping function') to the integral in eq. 3, ω(r), which is not grounded in physical considerations about the RDF. One such window function is used by Lorch :