Dear all, please help I get a different conductance plot every time by executing the same program. i didnot change anything in the program. Whats the problem? Please help me import kwant import numpy as np from matplotlib import pyplot import matplotlib.pyplot as plt import numpy as np import numpy.linalg as npl import scipy.sparse.linalg as sla import os output_directory="output" def saveoutput(fname, datatuple, header=""): fname2 = os.path.join(output_directory, fname) np.savetxt( fname2, np.column_stack(datatuple), fmt="%.6e", delimiter="\t", header=header ) def set_pub(): plt.rcParams.update({ "font.weight": "bold", # bold fonts "font.size":18, #"tick.labelsize": 15, # large tick labels "lines.linewidth": 2, # thick lines "lines.color": "k", # black lines "grid.color": "0.5", # gray gridlines "grid.linestyle": "-", # solid gridlines "grid.linewidth": 0.5, # thin gridlines "xtick.major.size":10, "xtick.minor.size":5, "ytick.major.size":10, "ytick.minor.size":5, "savefig.dpi": 600, # higher resolution output. }) Wnr=99 lnr=60 a=2.46 lat=kwant.lattice.honeycomb(a,norbs=1) a,b=lat.sublattices def rect(pos): x,y=pos return 0<=x<=lnr and 0<=y<=Wnr def delet(pos): x, y = pos return 0<=x<=39 and 20<=y<=80 # for 20 atoms x is 35 , #for 17 atoms x is 39 # for 23 atoms x is 31, #41 for 15 atoms #for 14 atoms ===42 def onsite(site, voltage): x, y = site.pos return voltage model1 = kwant.Builder() model1[lat.shape(rect,(1,1))] = 0 model1[lat.neighbors()] =2.64 del model1[lat.shape(delet, (11,25))] model1.eradicate_dangling() ###########lead 1############# def lead1_shape(pos): x, y = pos return 0<y <=20 def lead2_shape(pos): x, y = pos return 80<=y<=Wnr sym = kwant.TranslationalSymmetry(lat.vec((-1,0))) #from the left sym.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) lead = kwant.Builder(sym) lead[lat.shape(lead1_shape, (1,2))]=onsite lead[lat.neighbors()] =2.64 model1.attach_lead(lead) ########### lead 2 ################# sym1 = kwant.TranslationalSymmetry(lat.vec((-1,0))) #from the left sym1.add_site_family(lat.sublattices[0], other_vectors=[(-1, 2)]) sym1.add_site_family(lat.sublattices[1], other_vectors=[(-1, 2)]) lead2 = kwant.Builder(sym1) lead2[lat.shape(lead2_shape, (2,82))]=0 lead2[lat.neighbors()] = 2.64 model1.attach_lead(lead) model1.attach_lead(lead2) model1=model1.finalized() kwant.plot(model1,dpi=300) set_pub() plt.rc('axes', linewidth=2.0) plt.savefig('output\\Ushape.tif',bbox_inches='tight',dpi=300) ##################calculations################### ###functions for calculations params = dict(voltage_lead=0,voltage=0) kwant.plotter.bands(model1.leads[0], params=params) #bandstructure of lead set_pub() plt.rc('axes', linewidth=2.0) pyplot.xlabel("K",fontweight='bold') pyplot.ylabel("Energy",fontweight='bold') plt.show() plt.savefig('output\\Ushape_1st_lead.png',bbox_inches='tight',dpi=300) def plot_conductance(sys, energies, params=params): # Compute transmission as a function of energy data = [] for energy in energies: smatrix = kwant.smatrix(sys, energy, params=params) data.append(smatrix.transmission(0, 1)) pyplot.figure() pyplot.plot(energies, data) pyplot.xlim([-3,3]) pyplot.grid(which='major', color='#DDDDDD', linewidth=1.2) pyplot.grid(which='minor', color='#EEEEEE', linestyle=':', linewidth=1) pyplot.minorticks_on() #pyplot.grid(which='minor') pyplot.ylim([0,4]) pyplot.xlabel("Energy (eV)",fontweight='bold') pyplot.ylabel("Conductance $(e^2/h)$",fontweight='bold') set_pub() plt.rc('axes', linewidth=2.0) pyplot.show() plt.savefig('output\\Ushape_cond.tif',bbox_inches='tight',dpi=300) return data #plot_conductance(model1,eng) ################DOS KPM################################## rho = kwant.kpm.SpectralDensity(model1, params=params) energies, densities = rho.energies, rho.densities plt.figure() plt.plot(energies, densities) plt.savefig('output\\Ushape_DOS.png',bbox_inches='tight',dpi=300) ######################################### data=plot_conductance(model1,energies, params=params) saveoutput('c_shape.dat',(energies,data)) Thanking You