Dear Patrizio
Are you sure you need ecutwfc=100 Ry and ecutrho=12*ecutwfc to
converge US pseudopotentials? Have you performed convergence tests on
simple systems or flicked through sssp tables (I see 30/240 for
pslibrary US Mg and 40/320 for gbrv US Sb...)?
However, for your nscf step you require a 45 45 31 k-points mesh. It's
a lot of k-points. I don't know what is the purpose of your
calculations, so I can't say if you are uselessly oversampling the
Brillouin zone. But there is no free lunch...
HTH
Giuseppe
PS maybe we are nearest neighbours, you may phone... :-D
Quoting patrizio.grazi...@cnr.it:
Hello everybody,
I'm seeking advice to fasten nscf convergence (or make it possible).
I'm using qe 6.8 to study Mg3Sb2 / Mg3Bi2 solid solutions, as first
step I'm starting with a Mg3Sb2 2x2x2 supercell (40 atoms) to
compare with simple Mg3Sb2 cell (5 atoms).
The calculation track is scf --> nscf --> fs.
For the simple cell it runs smoothly (and I'm confident it is okay
as I compared with a colleague of mine relatively expert in DFT, not
qe).
For the supercell the scf converges in around 1 day of CPU time, but
the nscf does not converge in ~ 12 days of CPU time - say 23 hours
with 4 nodes, 6 tasks, 6 cpu-per-task, npool=24, are not sufficient
to reach convergence.
I attach the .in files for both scf and nscf, as well as the nscf
out file. There are several eigenvalues not converged but I am not
sure if this is the cause of the long time required for convergence
(I've read in the forum this can be often regarded as a warning).
So, since I have limited computational resources, before making many
trial-and-error attempts I would seek hints and advices to
understand if it is only a matter of make a more intensive
calculation (I've read the restart mode is not recommended for nscf
so I should ask for more nodes), or to improve the input file in an
aware way.
Sorry if this is a time waste for you, and thanks in advance for any support,
Patrizio
--
Patrizio Graziosi, PhD
Research Scientist
CNR - ISMN
Institute for the Study of Nanostructured Materials
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.matti...@ism.cnr.it>
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