Thank you Giovanni!
And as a reminder to everyone, there is the Quantum ESPRESSO input
generator on the Materials Cloud that can offer some sanity checks - you
upload a structure, and it tells you a reasonable set of input
parameters and pseudopotential suggestions:
https://qeinputgenerator.materialscloud.io
nicola
On 30/09/2025 10:03, Giovanni Cantele wrote:
Hi,
first of all, I suggest checking your input structure. The input files
you attached are in html format, so
it is difficult for me to try to open the file using programs able to
visualize the structure. This is the first task to
be done before running any calculation.
Second, you said you did several trials, but you did not say which! So,
it is difficult to suggest what to change
if we do not know what you did.
Third, there is no output file, which also might be helpful in trying to
figure out what's happening. For example: did you plot
the bands "as are" or you shifted by the proper Fermi energy? Are you
sure that you are not seeing the wrong energy interval?
Fourth, after a quick inspection of your inputs (that in html format are
a mess!) , it seems to me that a 120 Ry ecutwfc is too high for a PAW
pseudopotential.
If you reduce it, then reduce ecutrho accordingly.
As far as the question about the basis set is concerned, it is a long
standing problem. With localized basis sets you reduce significantly the
computational cost
of the calculation, but you should be aware of numerical problems
related to basis set size, non orthogonality of orbitals, systems where
you need basis set functions
located not at atomic positions, and so on. A plane-wave basis set is
numerically more expensive, but allows you to control the convergence
with respect to the
basis set using a single parameter, the cutoff (ecutwfc in QE). Being a
basis set of functions which are delocalized, a side effect is that they
are non zero also in the vacuum regions
where you expect nearly zero charge density. However, this turns out to
be also an advantage, because it means that the basis set has no
"spatial dependence", that is, given the unit cell and
the cutoff(s), it is independent on the atomic species and/or positions
you put therein.
If you provide more details, we could try to understand whether or not
your calculation is wrong.
Giovanni
--
Prof. Giovanni Cantele
Dipartimento di Fisica "Ettore Pancini"
Universita' degli Studi di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele@unina
Phone: +39 081 676910
Web page: https://sites.google.com/view/giovanni-cantele/home <https://
sites.google.com/view/giovanni-cantele/home>
Il giorno mar 30 set 2025 alle ore 09:23 Jodan Ebaya
<[email protected] <mailto:[email protected]>> ha scritto:
Good day!
I am Jordan Lee Ebaya, a second MS-PHYSICS students of Mindanao
State University Iligan Institute of Technology, Iligan CIty,
Philippines. Currenlty i am working with my graduate research which
Focus on DFT calculation using Qunatum Espresso.
I just want to ask if my input files in QE is wrong since i already
have done several trials and still i did not get the result i
wanted. Base on the journal Iread that was publish on RSC, thier
calcualtion shows that there is a 0.3eV bandgap of the Magnesium
Dicarbide using Amsterdam Desnity Functional Simulation Package ADF-
BANDS with Slater Type Orbital, Double Zeta Polarized Basis set. I
also want to know, what are the cons and pros of using differenet
basis sets?
Attached documents are my relax, scf, nscf(bands) input file and the
resulted bands strutre.
Thank you and hoping for an answer for this inquery, this will be a
great help for my thesis.
Sincerely,
Jordan Lee P. Ebaya
/MS-PHYSICS Students/
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----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, SNSF
Laboratory Head, PSI Center for Scientific Computing, Theory, and Data
Contact info and websites: https://theos-wiki.epfl.ch/en/Main/Contact
_______________________________________________________________________________
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worldwide who are victims of terrorism, military aggression, and indiscriminate
warfare.
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