t = 0 pb = ProgressBar(0, Nsteps, c="blue", ETA=0) for i in pb.range(): y_eu, v_eu = euler(y_eu, v_eu, t, dt) y_rk, v_rk = rk4(y_rk, v_rk, t, dt) t += dt positions_eu.append(y_eu) # store result of integration positions_rk.append(y_rk) pb.print("Integrate: RK-4 and Euler") #################################################### # Visualize the result #################################################### vp = Plotter(interactive=0, axes=2) # choose axes type nr.2 vp.ytitle = "u(x,t)" vp.ztitle = "" # will not draw z axis for i in x: vp += Point([i, 0, 0], c="green", r=6) pts_actors_eu = vp.actors # save a copy of the actors list pts_actors_eu[0].legend = "Euler method" vp.actors = [] # clean up the list for i in x: vp += Point([i, 0, 0], c="red", r=6) pts_actors_rk = vp.actors # save a copy of the actors list pts_actors_rk[0].legend = "Runge-Kutta4" # merge the two lists and set it as the current actors vp.actors = pts_actors_eu + pts_actors_rk
return 1j * (nabla2psi - V * psi ) # this is the RH of Schroedinger equation! def d_dt(psi): # find Psi(t+dt)-Psi(t) /dt with 4th order Runge-Kutta method k1 = f(psi) k2 = f(psi + dt / 2 * k1) k3 = f(psi + dt / 2 * k2) k4 = f(psi + dt * k3) return (k1 + 2 * k2 + 2 * k3 + k4) / 6 vp = Plotter(interactive=0, axes=2, bg=(0.95, 0.95, 1)) vp.xtitle = "" vp.ytitle = "Psi^2(x,t)" vp.ztitle = "" bck = vp.load(datadir + "images/schrod.png").alpha(.3).scale(.0255).pos( [0, -5, -.1]) barrier = Line(np.stack((x, V * 15, np.zeros_like(x)), axis=1), c="black", lw=2) lines = [] for i in range(0, Nsteps): for j in range(500): Psi += d_dt(Psi) * dt # integrate for a while before showing things A = np.real(Psi * np.conj(Psi)) * 1.5 # psi squared, probability(x) coords = np.stack((x, A, np.zeros_like(x)), axis=1) Aline = Line(coords, c="db", lw=3) vp.show([Aline, barrier, bck])