Ok, so this is not some unproblematic numerical artifact?
Here are some details:
There still version 11.2.3 at the cluster where I did those calculations. The calculations itself were done quite some time ago, too. It is just now, that I calculated the effective potentials from the saved SCF-states. However, I have attached a minimal script with my simulation parameters (the saved SCF-state would be much too large). I created the script by dragging the calculated configuration into the VNL-scripter. This should keep all the parameters. I did not yet include the part for taking the averages along the A- and B-direction but.
But note: Redoing the calculation is very time consuming given the big size of the system (the vacuum gap could be decreased but it would still take its time).
Some further explanations:
The previously posted effective potential was for copper. I tried the same for Aluminium, Palladium, Siver, Platinum and Gold.
Silver and Gold did not work at all (segmentations fault). I have absolutely no idea why this is so! (If you can tell me a nice way to send you a 200Mb file, then you can try it out on your own.) The other metals run and I get results.
There is alway such a spike at the right boundry, except for aluminium!!! This one is okay.
Well, I was quiet dissatisfied with the situation, but luckily I had saved non-selfconsistent device calculations, too (that is: only the effective-bulk calculations). I have quite some metal to the left and to the right, so that the screening condition should be matched very well, so I think I can use those and get comparable results.
Everything worked out fine (and this time there was no seg. fault when calculating the eff. pot. of gold or silver). The good news: results are very much the same compared to the self-consistent run. The bad news: The peak at the right boundary is reproduced, too.
One final note: I have the feeling this issue could be related to the Poisson solver? I use FFT for the electrodes and FFT2D for the devices. Is that okay???
But even if not: how would that explain why there is a peak in the non-selfconsistent results, too?