Dear Kwant user, I am trying to buil an extended system (supercell) by only defining its lattice vectors and its unit cell coordinate. After doing that whenever I am trying to plot the system, I am getting the following error : Traceback (most recent call last): File "practice.py", line 49, in <module> kwant.plot(syst) File "/usr/lib/python3/dist-packages/kwant/plotter.py", line 834, in plot sites_pos = sys_leads_pos(syst, sites) File "/usr/lib/python3/dist-packages/kwant/plotter.py", line 475, in sys_leads_pos num_lead_cells = site_lead_nr[-1][2] + 1 IndexError: list index out of range ______________________________________________________________ Nothing has been mentioned in the Kwant manual. I am also pasting the python code which I am trying to run : import kwant import matplotlib.pyplot from math import sqrt syst = kwant.Builder() # Defining the lattice sin_45 = 1 / sqrt(2) cos_45 = 1 / sqrt(2) lv=1 lat=kwant.lattice.general([(0,1),(1,0)],[(cos_45/2,sin_45/2),(cos_45/2+1,sin_45/2),(cos_45/2+1,-sin_45/2),(cos_45/2,-sin_45/2)]) a, b, c, d = lat.sublattices t = 1.0 W=10 L=10 syst = kwant.Builder() def make_cuboid(W=10, L=10): def cuboid_shape(pos): x, y = pos return 0 <= x < W and 0 <= y < L syst = kwant.Builder() syst[lat.shape(cuboid_shape, (0, 0))] = None syst[lat.a.neighbors()] = -0.5 syst[lat.b.neighbors()] = 0.5 syst[lat.c.neighbors()] = -0.5 syst[lat.d.neighbors()] = 0.5 return syst kwant.plot(syst) I am requesting you to help me in this regard. Also please let me know how should I attach leads according to my choice in the above system. -- *Dr. Suman Chowdhury* *Assistant Professor Dept. of Physics, Bangabasi College Kolkata- 700009, West Bengal, India.* * Ph no-+91-9830512232*