[gpaw-users] GPAW calculation crashes with adsorbates on jellium of certain geometries

[Rasmus Karlsson]

Dear Mikkel,
thank you for your reply. I can certainly do the calculations in grid
mode, but considering how much faster PW mode is, it would be a nice feature if it would be mode-agnostic. Is it difficult to get it to
work in PW mode? Still, the userbase for
jellium is perhaps too limited for that to be interesting. In any case,
we should look at adding an assertion that checks that the calculation
is running in grid mode and not in PW mode.

However, I actually found something else related to jellium calculations that is
strange (explaining the new title of this thread). I'm attaching the script that I'm looking
at. Apparently, if you combine the dimensions of the slab, the
Wigner-Seitz radius and the adsorbate identity in an unfortunate way, the code crashes.

If you set the flag use_higher_b to True (making the slab bigger), the code will crash for H, He,
Li and Be (but not B or C, see below) with the
following error:

"
    correct_for_charge(f_j, charge, degeneracy_j, True)
  File "/Users/rasmusk/Library/Python/2.7/lib/python/site-packages/gpaw/setup.py", line 142, in correct_for_charge
    if charge >= 0:
RuntimeError: maximum recursion depth exceeded in cmp
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /Users/rasmusk/Library/Python/2.7/lib/python/site-packages/gpaw/setup.py(142)correct_for_charge()
-> if charge >= 0:
"

However, if you either use a lower b ("use_higher_b = False", lowering
the number of electrons in each cell since the slab is smaller) or use a higher wigner-seitz radius
("use_higher_rs = True", also reducing number of electrons in the slab
in each cell), the code works. Strangely,
if a heavier adsorbate is used (B or C in the attached example code), the
code also runs. The error does not seem to be related to whether or not
the dimensions of the jellium slab are evenly divisible with the grid spacing
(since setting use_dimensions_evenly_divisible_w_h to either True or
False has no effect on the error).

This error message was apparently encountered by someone before (https://listserv.fysik.dtu.dk/pipermail/gpaw-users/2012-July/001635.html)
but that was not related to a jellium calculation. I guess this points
to some kind of issue in how GPAW handles certain (small?) initial
electronic densities. 

Thanks,
Rasmus


Mikkel Strange writes:

> Dear Rasmus,
>
> thanks for pointing this out.
> I'm afraid that GPAW can only do grid mode calculations for jellium systems (except for bulk system where plane wave mode should also work). 
> I think the reason why it does not work in PW mode is that it "throws away"  the  density profile specified in the 
> JelliumSurfacePoissonSolver.
>
> Can you do the calculations in grid mode, or do you need the PW basis?
>
> In any case, at least an error message when trying to use PW would nice :-)

-- 
Rasmus Karlsson, PhD



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