Dear kwant users, Hello, I am a new user of kwant, I want to build a 3d structure model, and add leads, I refer to a similar code, but I keep getting errors during the process, the program says "RuntimeError: All sites of this builder have been deleted because an exception occurred during the execution of fill(): see above. ", I feel that it may be the position of the lead, but I do not know how to modify it, can you give me some suggestions to modify it? Thank you very much! *This is the code I have errors in: ---------------------------------------- import kwant import numpy as np from matplotlib import pyplot #3d test def syst_3d(a=16, b=16, c=10,t=1): lat = kwant.lattice.general([(0, 0.5, 0.5), (0.5, 0, 0.5), (0.5, 0.5, 0)]) # [(0,0,0),(0.25, 0.25, 0.25)]) # a,b= lat.sublattices syst = kwant.Builder() def cuboid_shape(pos): x, y, z = pos return 0 <= x < a and 0 <= y < b and 0 <= z < c syst[lat.shape(cuboid_shape, (0, 0, 0))] = 4 * t syst[lat.neighbors()] = -t sym_lead0 = kwant.TranslationalSymmetry(lat.vec((1, 0, 0))) lead0 = kwant.Builder(sym_lead0) lead_shape = lambda pos: (-b / 2 <= pos[1] < b / 2) and abs(pos[2]) < c lead0[lat.shape(lead_shape, (-1, 0, 0))] = 4 * t lead0[lat.neighbors()] = -t lead1 = lead0.reversed() syst.attach_lead(lead0) syst.attach_lead(lead1) return syst def main(): syst = syst_3d() kwant.plot(syst) if __name__ == '__main__': main() --------------------------------------------------- *This is the code I refer to, as if this works correctly: ------------------------------------------------------- import kwant import numpy as np from matplotlib import pyplot def syst_3d(W=3, r1=2, r2=4, a=1, t=1.0): lat = kwant.lattice.general(((a, 0, 0), (0, a, 0), (0, 0, a))) syst = kwant.Builder() def ring(pos): (x, y, z) = pos rsq = x**2 + y**2 return (r1**2 < rsq < r2**2) and abs(z) < 2 syst[lat.shape(ring, (0, -r2 + 1, 0))] = 4 * t syst[lat.neighbors()] = -t sym_lead0 = kwant.TranslationalSymmetry(lat.vec((-1, 0, 0))) lead0 = kwant.Builder(sym_lead0) lead_shape = lambda pos: (-W / 2 < pos[1] < W / 2) and abs(pos[2]) < 2 lead0[lat.shape(lead_shape, (0, 0, 0))] = 4 * t lead0[lat.neighbors()] = -t lead1 = lead0.reversed() syst.attach_lead(lead0) syst.attach_lead(lead1) return syst def main(): syst = syst_3d() kwant.plot(syst) if __name__ == '__main__': main() Sincerely, Yue Xiang