Hi Giuseppe,
thanks a lot for your time and support!
The answer to the first question is honestly no, I took ecutwfc to a
colleague of mine (for simple cell, not supercell) and ecutrho for
USPP from the qe indications, I'll work on this.
For the sampling, the final purpose is transport calculations and I'm
afraid this sampling can be already too rough. If it's too much, I'll
go for Wannier, for which unfortunately I've no experience (not yet).
I'll follow your indications and, if the case, I'll feel free to phone you :D
Thanks!!!
Patrizio
Giuseppe Mattioli <[email protected]> ha scritto:
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 [email protected]:
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: <[email protected]>
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--
Patrizio Graziosi, PhD
Research Scientist
CNR - ISMN
Institute for the Study of Nanostructured Materials
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