Three comments:
RMT consistency is in particular important for total energies. If you
compare the energy of 2 phases and their energy difference is just a few
mRy, make sure you really have consistent RMTs and RKmax. Since the
scaling with RKmax is not perfect, it might be wrong enough to lead to a
wrong ground state (in particular when you are using a rather low RKmax
value - with a fully converged RKmax the RMT dependency is reduced
(except for possible core leakage !)
You mentioned core level shifts. This is something you simply have to
test yourself. My expectation is, that it is NOT very crucial, as long
as you have at least "similar" convergence. Calculate the core level
shifts for one compound with large and small RMT and compare the
results. If they are the same within acceptable errors, you can forget
RMT problems for this property.
I'd expect that this should be general enough except when you have a
very exotic compound.
lmax is uncritical, but for larger spheres lvns may have a larger
influence as well as linearization errors (HDLOs for d or f electrons
and large spheres), while GMAX may also be important for small spheres.
Am 08.04.2021 um 07:18 schrieb Pavel Ondračka:
Thank you Laurence,
I was a bit worried because the FAQ you linked also says: "Of course
you should use identical Mg+O spheres for MgO and Mg(OH)2 for
consistency", so I was not 100% sure if keeping the same maximum K-
vector Kmax is enough.
Should I also increase lmax and lvns for the larger spheres somehow? Or
would you keep it the same for small and large N spheres?
Best regards
Pavel
On Wed, 2021-04-07 at 15:33 -0500, Laurence Marks wrote:
Have a look at http://www.wien2k.at/reg_user/faq/rkmax.html. If (say)
with an RMT for the N of 1.6 a RKMAX of 6.5 is good enough, then when
you reduce the RMT to 1.3 you can reduce the RKMAX to 6.5*1.3/1.6 =
5.28. This will not give you precisely the same relative convergence,
but is close.
Another way is to say that an RKMAX of 7 is "OK" for RMTs of 2.0, an
RKMAX of 3 for RMTs of 0.5, then interpolate using a straight line.
This is similar.
On Wed, Apr 7, 2021 at 3:24 PM Pavel Ondračka
<pavel.ondra...@email.cz> wrote:
Dear Wien2k mailing list,
I have a series of TiN and TiON amorphous-like structures where I
have
some large differences in spheres sizes for N atoms. In most of the
structures the smallest N sphere is around 1.6-1.7, however in some
I
have few N atoms with 1.3 (the structures should be OK, this much
smaller size is due to some rare local configuration which would
correspond to something like N split interstitial in crystalline
structure).
My goal is to calculate core electron binding energies of N1s
levels
of
many atoms in the structures (at least 200 core-hole calculations)
and
I need to be consistent over different structures in the series.
So usually I would just check what is the smallest N sphere size in
the
whole set, and force it for all N atoms in all structures and than
use
the identical RKmax for all structures, just to be sure I'm
consistent.
This is unfortunatelly not very efficient with respect to the
calculation speed as I have quite large cells (around 150 atoms).
Is
there another way how can I save some CPU time and keep the
consistency?
I was for example thinking if I can force somehow two different N
sphere sizes (one for the N split intestitial, which I have usually
just one in the whole cell and one larger for the rest of N atoms),
than I would have consistent sphere size for the rest of N atoms in
the
series and I could change the RKmax to keep the same largest K-
vector
which should be enough to guarantee consistency for all N atoms
expect
the split interstitials (but I don't care that much about them).
However as far as I understand this is not possible?
Any ideas would be appreciated.
Best regards
Pavel Ondracka
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