HartreeDifferencePotential caculation

[Steven Lin]

Hello, I recently wanted to reproduce the results from this tutorial: https://docs.quantumatk.com/tutorials/ag_si_interface/ag_si_interface.html, but I encountered an issue when calculating the HartreeDifferencePotential. I used the provided `device.py` script and configured the calculator exactly as described in the example. However, after the calculation completed, the output showed the following pattern: the potential values at both the start and end points are 0 eV, while the potential in the middle region is exceptionally large. Additionally, there are no signs of convergence even after 400 steps. Should I try increasing the number of steps to see if convergence can be achieved, or is there a mistake in my calculation settings?\

[Anders Blom]

Maybe check the electron temperature,  the default was 300 K when the tutorial was written, now it's 1000 K, maybe that causes convergence problems. We will also check ourselves if the calculation settings are still correct, the tutorial is 9 years old and some adjustments may be needed for newer versions of the code.