[QE-users] Inquiry Regarding Crystal Structure Discrepancy in Quantum Espresso

[Giovanni Cantele]

As I infer from the input you sent me, if you take atomic positions,
designed to fill the unit cell of a simple tetragonal crystal and use the
same to fill the sites of a body centered tetragonal lattice, you'll
definitely obtain two different structures, one should worry in the case
they look equal!

What you should observe is that your atomic positions are "redundant" in
that if instead of replicating them on the sites of a simple tetragonal
lattice you replicate a fraction of them on the sites of a body centered
lattice, then the two resulting structures are the same. In this case,
since the st primitive cell has twice the volume of a bct primitive cell,
you should halve the positions (of course removing the ones equivalente by
a translation of the bct lattice), then ibrav=7 will definitely work.
BEWARE: your positions are in crystal units. That means they are expressed
in units of a1,a2,a3 of the st lattice. As such, besides halving the number
of atoms, you have to change also the positions of the remaining ones, if
you keep crystal as units (because a1',a2',a3' of bct are different from
a1,a2,a3 of st), otherwise convert them in Angstrom first.

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
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno sab 30 dic 2023 alle ore 17:03 houssam eddine hailouf <
h.hailouf at yahoo.com> ha scritto:

> Please sir if I can proceed my calculations with ibrav =6 and if this
> state is correct " 7 is for body centered tetragonal. 6 is for primitive
> one"
>
> My problem,
> but when I write Ibrav =7 and I use xcrysden to visualize the structure I
> found other structure and when I write Ibra =6 I find the relevant
> structure.
>
> Sincerely
> Hailouf
>
>
> Le sam., déc. 30, 2023 à 16:20, Giovanni Cantele
> <giovanni.cantele at spin.cnr.it> a écrit:
> and what is the file with ibrav=7 that gives you incorrect results?
> GC
> --
>
> 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
> Web page: https://sites.google.com/view/giovanni-cantele/home
>
>
> Il giorno sab 30 dic 2023 alle ore 16:07 houssam eddine hailouf <
> h.hailouf at yahoo.com> ha scritto:
>
> Hi dear Giovanni
>
> Please find my input file attached below such as the system under
> consideration is body-centered tetragonal crystal structure (I41md), but
> when i display the crystal structure with ibrav= 7 i get wrong crystal
> structure but it's fine with ibrav=6.
>
> Sincerely
> Hailouf
> Le samedi 30 décembre 2023 à 14:38:13 UTC+1, Giovanni Cantele <
> giovanni.cantele at spin.cnr.it> a écrit :
>
>
> Dear Hailouf,
>
> I think it is not easy to help you with the information you provided.
> 1) What do you mean with "an incorrect crystal structure"? Is
> Quantum-ESPRESSO giving a structure you do not expect or the calculation
> fails for some other reason? In the case, what is the "error" provided by
> the code?
> 2) In ibrav=6 produces the "correct structure", then your structure is
> simple tetragonal? Or you are trying to reproduce a body-centered
> tetragonal structure using a simple tetragonal unit cell?
>
> With some more detail (and/or input/output files), maybe a more helpful
> answer could be issued.
>
> 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
> Web page: https://sites.google.com/view/giovanni-cantele/home
>
>
> Il giorno sab 30 dic 2023 alle ore 14:05 houssam eddine hailouf via users <
> users at lists.quantum-espresso.org> ha scritto:
>
> Dear Quantum Espresso Group,
>
> I am currently studying systems within the body-centered tetragonal
> structure. I've encountered an issue where setting ibrav = 7 yields an
> incorrect crystal structure, while using ibrav = 6 produces the correct
> structure, and calculations proceed smoothly. Could you provide any
> insights or explanations regarding this situation?
>
> Thank you,
> Hailouf houssam
> Materials Science and Informatics Laboratory, Djelfa algerie.
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
> --

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
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno sab 30 dic 2023 alle ore 14:05 houssam eddine hailouf via users <
users at lists.quantum-espresso.org> ha scritto:

> Dear Quantum Espresso Group,
>
> I am currently studying systems within the body-centered tetragonal
> structure. I've encountered an issue where setting ibrav = 7 yields an
> incorrect crystal structure, while using ibrav = 6 produces the correct
> structure, and calculations proceed smoothly. Could you provide any
> insights or explanations regarding this situation?
>
> Thank you,
> Hailouf houssam
> Materials Science and Informatics Laboratory, Djelfa algerie.
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
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