Dear Prof. Blaha, Marks,
Thank you for your comments, they solved my problem immediately!
It "magically" works with init_lapw -prec 1 -ecut 0.999 :-)
Why -ecut 0.999 and not -ecut 1? Is the consequence of this only in not
having core-levels (I don't need them in this case)?
I converged, and then continued with a larger klist, but the results are
nearly identical.
WTe2 that I am calculating is semimetallic, therefore I used -prec 1 and
not -prec 1n. Also, I am replicating what has been already calculated by
several groups (for the purpose of a more detailed spin/orbital
character study), therefore I know what the result for the band energies
should be.
Best,
Lukasz
On 2023-06-17 08:47, Laurence Marks wrote:
In addition to what Peter said, pay careful attention to how you setup
the slab calculation. WTe2 has a band gap of 1.0 eV, and it may be
less with PBE. I suggest checking your bulk band gap first.
With a small gap surface, TEMPS is needed and getting the positions
right (-min) and a valence neutral surface will matter. You will need
to converge density and positions without soc. If you don't setup the
surface right GIGO and if will be horribly unstable. (STIFF in
case.inm may help.) With GIGO the physics is wrong so your
calculations will be meaningless.
---
Professor Laurence Marks (Laurie)
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu [1]
"Research is to see what everybody else has seen, and to think what
nobody else has thought" Albert Szent-Györgyi
On Sat, Jun 17, 2023, 09:01 Peter Blaha <peter.bl...@tuwien.ac.at>
wrote:
Your 4 points are not really recommended in the first place.
If it is a scf convergence problem (which I doubt): grep:DIS
case.scf
. Does it look like divergence ?
You need to find which eigenvalue causes the ghostband, from which
atom
and angular momentum.
See *scf2* and *output2* files.
Once you know this, look into case.scf1 to see how the LOs and
energy
parameters for this state are set and you probably have to modyfy
case.in1(c).
PS: Use init_lapw -prec 1n at the beginning, maybe with -ecut
0.999 .
PS: I would NOT include HDLOs, if I had ghostbands. Mixing with
PRATT
helps only in very few cases, not really recommended for "normal"
calculations.
PPS: I hope you use runsp_c_lapw for something like WTe2 ?
Am 17.06.2023 um 00:28 schrieb pluto via Wien:
Dear Prof. Blaha, dear All,
Thank you for the comment on slab strategy, this helps a lot.
I have more specific question: for a large WTe2 slab (60 atoms),
which
is a material of low-symmetry that has a polarity also in the
out-of-plane direction, I am getting ghostbands in lapw2 after few
iterations. What is a good strategy to fix this?
I was thinking of:
1. init_lapw -hdlo
2. Low mixing (like 0.05) with PRATT
3. Decrease RMT (from first tests, with RMT 2.5 ghostbands seem to
appear after around 3 iterations, with 2.2 after many iterations)
4. Increase RKmax
3 and 4 are probably computationally expensive...
I did several tests without SOC, I was typically using something
like:
init_lapw -sp -b -numk 100 -hdlo -fermit 0.002
Maybe other settings are critical?
Bulk calculation converges very easily (first without and then
with
SOC) with default settings like
init_lapw -sp -b -numk 2000
bulk bands look like the literature, and are practically the same
with
RMT 2.2 and RMT 2.5.
Best,
Lukasz
On 2023-06-16 16:45, Peter Blaha wrote:
No,this is not a good strategy.
From a converged non-spin-polarized calculation you cannot come
(easily) to a spin-polarized solution.
So 1) is only good if you want to quote how much more stable a
SP
solution is compared to a non-SP.
2 + 3 is a good practice. You gain insight how large are the
changes
and on what atoms due to SO coupling.
------------------------
In terms of efficiency for large cases, I'd in particular
preconverge
with a course k-mesh and later on refine.
---------------------------
Every runsp cycle starts with a case.clmsum/up/dn file.
These files can come from an initialization, but of course also
from
any prior scf calculation (eg. with lower k-mesh or without SO).
Of
course, a restore_lapw ... gives you all files necessary to run
another scf cycle.
-NI would keep old broyden files, but after a "save_lapw" they
are
gone anyway. -NI is useful if you want to continue a scf,
because eg.
the first runsp stopped after 40 cycles and did not reach
convergence
yet.
Am 16.06.2023 um 10:44 schrieb pluto via Wien:
Dear All,
I just would like to confirm the step-by-step convergence
strategy
for the large slab with SP and SOC (it refers in general to
spin-momentum locked non-magnetic TMDC, but can be any other
material).
Is the following correct:
1. Converge without SP and without SOC, and save_lapw e.g. as
CONV_NO_SP_NO_SOC so it can be used in another directory or on
another computer for the next steps
2. Use this as a starting point to converge with SP, and
save_lapw
as CONV_W_SP_NO_SOC (one can also restore_lapw in another
directory
and start there)
3. Use this as a starting point to converge with SP and with SOC
(and save_lapw to have it for the future)
I often start with step 3 right away, but I think for a really
large
system this might be really inefficient.
How does the program know to use the starting density from the
previous step?
Does restore_lapw creates the necessary files when I transfer to
the
new directory?
Is -NI or some other setting in run_lapw important here?
At the moment I am using an older cluster with many cores and
use
k-parallel. Still didn't manage with MPI, but maybe it is not
needed
for what I want because my klist file is typically 50-80
k-points,
depending on the symmetry of the system. I use the QTL program
quite
a lot so having it parallellized would sometimes speed the
things up
a bit for me.
Best,
Lukasz
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--
-----------------------------------------------------------------------
Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email: peter.bl...@tuwien.ac.at
WWW: http://www.imc.tuwien.ac.at WIEN2k: http://www.wien2k.at
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