Hello, I have just started working with KWANT but at the beginning I have a problem with the calculation of the energy band in lead. Blow I paste my code in which a define the lead and try to calculate the energy vs wave vector. The definition of the lead comes from the example on the website documentation. I assume a lattice with the size dx and then t=h/m/dx/dx. The energy from the function kwant.bands is expresed in units of [t] and in this point a have a problem because if I define the lead with W=100 points and dx=0.1 nm and calculate the E vs k bands, it differs from the E vs k bands calculated for W=50 points and dx=0.2 nm (of course i scale the energy multiplying it by t), although the width of the lead W_eff=W*dx is the same for both cases. I would be grateful for any suggestions ? from matplotlib import pyplot import kwant import numpy import math f_nm2au=18.897261 f_eV2au=0.03674932587 f_Ha=27.2114 def make_lead(W=30,dx=1.0,m=0.0667): lat=kwant.lattice.square(dx) #uzupelnianie t=1.0/m/dx/dx sym = kwant.TranslationalSymmetry((-dx, 0)) lead=kwant.Builder(sym) lead[(lat(0,y) for y in range(-W+1,W))]=4*t lead[lat.neighbors()]=-t return lead ########## calculations for W=100 and dx=0.1 ############# lead=make_lead(W=100,dx=0.1*f_nm2au).finalized() band=kwant.physics.Bands(lead) momenta = numpy.linspace(-numpy.pi, numpy.pi, 101) energies = [band(k) for k in momenta] dx=0.1*f_nm2au m=0.0667 wsp=f_Ha/(m*dx*dx) #print len(energies[1]) f=open('mode_W100_dx01.dat','w') for i in range(len(momenta)): f.write("%f " % (momenta[i])) for j in range(len(energies[0])): f.write("%f " % (energies[i][j]*wsp)) f.write("\n") f.close() ########## calculations for W=50 and dx=0.2 ############# lead=make_lead(W=50,dx=0.2*f_nm2au).finalized() band=kwant.physics.Bands(lead) momenta = numpy.linspace(-numpy.pi, numpy.pi, 101) energies = [band(k) for k in momenta] dx=0.2*f_nm2au m=0.0667 wsp=f_Ha/(m*dx*dx) #print len(energies[1]) f=open('mode_W50_dx02.dat','w') for i in range(len(momenta)): f.write("%f " % (momenta[i])) for j in range(len(energies[0])): f.write("%f " % (energies[i][j]*wsp)) f.write("\n") f.close() Best Regards Pawel Wojcik