Dear developers of Kwant, I have seen most of the examples of Kwant usage, but somehow I miss the usage of functions to define the on-site energy of lattice sites in the leads. I have attached a simple Kwant script which includes the following lines ----------------- sym = kwant.TranslationalSymmetry((0, -1.)) lead = kwant.Builder(sym) lead[lat.shape(region_lead,(0.,0.))] = 4. + potential # use the same potential also for the lead !!! lead[lat.neighbors()] = -1. ------------------ the crucial line is the third one, where the function "potential" that defines the potential in the scattering region is used also in the lead. Since the leads are automatically attached to the scattering region I would expect that the potential is evaluated at the sites where the leads is attached and then repeated according to the translational symmetry given to the lead. Is this the case? I tried to check this using the "map" method in kwant.plotter, but the color in correspondence of the leads is an uninformative grey, which does not belong to the color scale used in the scattering region. Somehow in the documentation I was not able to find what happens when a function is used to define the onsite energy in a lead. Can you fill this gap? Thanks for your help in advance, Sebastiano