[QE-users] Problems with space-group and ibrav

[Javier GONZALEZ PLATAS]

Dear Andrii
Thanks for the information.

Just this afternoon doing trial and error I get that the best way for
passing the unit cell parameters is using
ibrav and celdim according with manual, and for passing the asymmetric unit
for atoms and their respective equivalents then I have to use the
space_group and uniqueb. So I think that is the same that you say in your
e-mail.

About value of  ecutwfc I have seen that depending of elements on your
structure I need to increase this value (but probably I understand
incorrectly). I have C, H, Cl, N, Cu and I, therefore using PBESOL PP I
have seen that ecutwfc should be 45-46 and not 80.

I'm starting to use QE so I need time to learn....

Thanks

Javier González Platas
Research_ID: I-1937-2015
Orcid: 0000-0003-3339-2998


Departamento de Física
Avda. Astrofísico Fco. Sánchez s/n
Apartado 456
38200 La Laguna. S/C de Tenerife

T. 922 318 251
M. 629 080 140
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El lun., 26 oct. 2020 a las 18:31, Andrii Shyichuk (<
andrii.shyichuk at chem.uni.wroc.pl>) escribió:

> Dear Javier,
>
> As the manual says, {ibrav=0}: "crystal axis provided in input: see card
> CELL_PARAMETERS".
> With ibrav=0, you only specify the cell parameters. Remove space_group and
> uniqueb, and specify all of the atoms in the cell.
>
> Alternatively, if you use space_group, you specify only the irreducible
> atoms (i.e. like in a cif file).
> But, you must specify celldm values and not CELL_PARAMETERS. Ibrav must be
> then non-zero and correspond to the space group. Also, make sure that you
> use uniqueb correctly.
>
> Also, I wonder why your ecutwfc is so high.
>
> Best regards.
> Andrii
>
> W dniu 2020-10-26 17:41, Javier GONZALEZ PLATAS napisał:
>
> Hello
> I'm trying to use space-group directive in order to give only the atoms in
> the asymmetric unit. But I don't know why I'm having problem with this.
> My partial code is
> ...
> &SYSTEM
>   !ibrav=0
>   space_group=14
>   uniqueb=.true.
>   nat=13
>   ntyp=6
>   ecutwfc=80.0
>   ecutrho=450.0
> /
> ....
> ....
> CELL_PARAMETERS (angstrom)
> 13.1164  0.0000  0.0000
>  0.0000  4.2363  0.0000
> -1.0566  0.0000 15.0983
>
> I have try to use ibrav=0 and without ibrav but always I have an error
> mensaje. The space group is 14 (P 21/c) What am I doing wrong?
>
> Thanks for help
>
> Javier González Platas
> Research_ID: I-1937-2015
> Orcid: 0000-0003-3339-2998
>
>
> Departamento de Física
> Avda. Astrofísico Fco. Sánchez s/n
> Apartado 456
> 38200 La Laguna. S/C de Tenerife
>
> T. 922 318 251
> M. 629 080 140
> ------------------------------
> Aviso de confidencialidad
> <https://www.ull.es/informacion-sobre-web-institucional/#aviso-confidencialidad>
>
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