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

[Andrii Shyichuk]

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 
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> 
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