Hi Ousmane, How can I make sure that there is no overlap between the lead and normal region? Lead_shape() returns -L <= x <= L and we want the lead to satisfy x <= 0. If we don't use color_site(site), then we would get the attached plot. The black region not only represents the normal region but also represents the lead. However, the lead may also cover the region of x > 0 as the function Lead_shape() suggests. Is there another way to check what part of the shape is scattering region, what part is lead? Thanks, -- A. Barış Özgüler PhD Candidate in Physics https://home.physics.wisc.edu/ozguler/ University of Wisconsin–Madison Madison, Wisconsin 53706, USA