[gpaw-users] Problems with Zn and Cd setups?

[Ask Hjorth Larsen]

Hi

2012/5/7 Jakob Schiøtz <schiotz at fysik.dtu.dk>:
> Hi,
>
> I noticed an extreme dependence of the lattice constants of Zn alloys when I vary the lattice spacing, and the energy of a simple Zn3Mg alloy varies a factor two when I vary the grid spacing between h=0.1 and h=0.18 Å!
>
> I then looked at the PAW setup page on the web.  The bond length of Zn varies wildly with h, see the third graph here: https://wiki.fysik.dtu.dk/gpaw/setups/Zn.html  It does not look like it converges at all.
>
> I looked a bit around, and found the same problem for Cd.  It looks like something is very wrong for these two elements.  The other neighboring elements have almost flat lines in these plots.
>
> Best regards
>
> Jakob

That is rather strange.  They (at least Cd) also seem to converge very
slowly in SCF loops, which is surprising given that the DOS at the
Fermi level is very low.  This weirdness goes away if the very short
projector cutoffs are changed to something more normal (--radius=2.45
for Cd).  So why would these elements need very short cutoffs?

Regards
Ask