[QE-users] Convergence not achieved

[Saiyed Tasnim Md Fahim]

Dear Dr. Cantele,

Thank you for your response.
I tried the steps that you mentioned. However, it still didn't converge.  I
am following this paper as the benchmark :
https://doi.org/10.1016/j.cej.2024.148940
I have used the norm conserving pseudopotentials from Pseudodojo website as
USPP/PAW wasn't implemented for TS dispersion. I used the ASE (atomic
simulation environment) to generate the atomic positions of the 2x2
supercell.

I have attached the new input file with this mail. Could you please tell me
if any parameters I have missed or need to be changed or removed? Thank
you.


Sincerely,
Saiyed Tasnim Md Fahim,
Ph.D. Student,
Environmental Engineering,
University of Southern California.


On Wed, Feb 28, 2024 at 12:27 AM Giovanni Cantele <
giovanni.cantele at spin.cnr.it> wrote:

> Dear Saiyed,
>
> when convergence issues show up there are several tricks you might
> consider, one of these is certainly reducing mixing_beta,
> another could be increasing degauss.
>
> However, before trying any trick to cure a calculation particularly
> difficult to converge, as a rule of thumb the first step is to
> check your input file parameters including cut-off, k-point grid, degauss,
> GEOMETRY, pseudopotentials, etc.
>
> After a quick look to your input file I can notice:
> - an incredibly huge value of degauss (1d-1 Ry = 0.1 Ry = 1.36 eV, this
> would smear even the band gap of silicon I think)
> - a mixing beta of 0.6, actually the advise of reducing it in cases of
> difficult convergence is meant to go down to even 0.1 or 0.05
> - but MOST IMPORTANTLY you specify ATOMIC_POSITIONS in crystal units, that
> are usually expected to be numbers in the range
> [-1,1] because in units of the lattice vectors there should be no reason
> to specify the position of an atom in a unit cell far apart from the
> origin. On the other hand, the numbers in your input file seem to indicate
> that you're actually giving the positions in Angstrom, because they are
> huge. If you try to visualize your input file using, for example XCrysDen,
> you can easily see atoms at incredibly huge distances. The geometry
> becomes much more reasonables if you replace "crystal" with angstrom.
> After doing that, recheck the geometry (with XCrysDen) to understand if it
> is
> what you expect or if there are still issues, before running any
> calculation.
>
> Giovanni
>
>
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it <giovanni.cantele at spin.cnr.it>
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
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>
> Il giorno mer 28 feb 2024 alle ore 08:41 Saiyed Tasnim Md Fahim <
> sfahim at usc.edu> ha scritto:
>
>> Dear users,
>> I am working with calcite in Quantum Espresso 7.1. I want to perform a
>> vc-relax calculation for 3 layers of calcite but after 100 iterations
>> convergence is not achieved. I changed the mixing beta but it did not work.
>>
>> I have attached the input file with this mail. Kindly let me know how I
>> should proceed for both the convergence.
>>
>> Sincerely,
>> Saiyed Tasnim Md Fahim,
>> Ph.D. Student,
>> Environmental Engineering,
>> University of Southern California.
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