Hello All, I am trying to simulate black phosphorous quantum dots of circular shape, but with their ends (that will be attached to the leads) will be broad. The shape would be something like a circle with two thick lines on either side of the circle. I have the following code for it, but the problem I face is that the two thick lines are disconnected from the circle. I am not able to understand the reason behind it and rectify it. If any of you could help me, it would be of great value to me. ------ CODE ------- *import kwant* *from matplotlib import pyplot* *import numpy as np* *h = 2.707 * np.cos(13.69*np.pi/180)* *dx = 4.43* *dy = 3.27* *shift_x = 2.164 * np.cos(0.5*98.15*np.pi/180)* *shift_y = 2.164 * np.sin(0.5*98.15*np.pi/180)* *r_const = 20* *lat0 = kwant.lattice.general([(dx, 0, 0), (0, dy, 0)], [(0, 0, 0), (shift_x, shift_y, 0)])* *lat1 = kwant.lattice.general([(dx, 0, 0), (0, dy, 0)], [(0.5*dx, 0.5*dy, h), (0.5*dx + shift_x, 0.5*dy + shift_y, h)])* *def cuboid_shape(pos):* * x, y, z = pos* * if -1.2*r_const <= x < -r_const:* * return abs(y) < r_const* * if -r_const <= x <= r_const:* * return x**2 + y**2 <= r_const**2* * if r_const < x <= 1.2*r_const:* * return abs(y) < r_const* *def potential(site):* * x, y, z = site.pos* * return (-tanh(5*(x-r_const)) - tanh(5*(x+r_const))) * pot* *sys = kwant.Builder()* *sys[lat0.shape(cuboid_shape, (0, 0, 0))] = potential* *sys[lat0.neighbors(1)] = 1* *sys[lat0.neighbors(2)] = 1* *sys[lat1.shape(cuboid_shape, (0.5*dx, 0.5*dy, h))] = potential* *sys[lat1.neighbors(1)] = 1* *sys[lat1.neighbors(2)] = 1* *lat0_0 = [ ]* *lat0_1 = [ ]* *lat1_0 = [ ]* *lat1_1 = [ ]* *for site in kwant.Builder.sites(sys):* * if site.family == lat0.sublattices[0]:* * lat0_0.append(site[1])* * elif site.family == lat0.sublattices[1]:* * lat0_1.append(site[1])* * elif site.family == lat1.sublattices[0]:* * lat1_0.append(site[1])* * elif site.family == lat1.sublattices[1]:* * lat1_1.append(site[1])* *for w in lat0_0:* * for v in lat0_1:* * for k in lat1_0:* * for l in lat1_1:* * if v == k:* * sys[lat0.sublattices[1](v[0],v[1]), lat1.sublattices[0](k[0],k[1])] = 2* * if w == l:* * if (w[0]+1,w[1]+1) in lat0_0:* * sys[lat0.sublattices[0](w[0]+1,w[1]+1), lat1.sublattices[1](l[0],l[1])] = 2* * if w == l:* * if (l[0]-1,l[1]-1) in lat1_1:* * sys[lat0.sublattices[0](w[0],w[1]), lat1.sublattices[1](l[0]-1,l[1]-1)] = 2* *kwant.plot(sys, site_size=0.2, hop_lw=0.1)* Any help would be greatly appreciated. Regards, Shivang Agarwal -- *Shivang Agarwal* Senior Undergraduate Coordinator - Academic Discussion Hours Discipline of Electrical Engineering IIT Gandhinagar Contact: +91-9869321451