[QE-developers] Space group does not produce correct Wyckoff positions

[Andrea Dal Corso]

I do not think there is an error. Please note that for centered
lattices the Bilbao Crystallographic Server as also the ITA tables give
the crystal coordinates in the basis of the primitive vectors of the
conventional unit cell, while QE writes on output the crystal
coordinates in the basis of the primitive vectors of the centered cell.

HTH,

Andrea

On Mon, 2020-08-24 at 14:07 +0000, 박민규 wrote:
> Dear all,
> 
> I found some Wyckoff positions are not correctly produced for space
> group I4/mmm (139) (ibrav=7).
> For example, if I assign 2b and 4d Wyckoff positions, QE 6.6 produces
> (0,1/2,1/2) for 2b and (1/2,3/4,1/4), (1/2,1/4,3/4) for 4d.
> 
> QE 6.6 with I4/mmm (139)
> 2b (0,1/2,1/2)
> 4d (1/2,3/4,1/4)
>      (1/2,1/4,3/4)
> 
> However as you can find from Bilbao Crystallographic Server<
> https://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list>, for
> I4/mmm (0,1/2,1/2) corresponds to 4c and (1/2,3/4,1/4), (1/2,1/4,3/4)
> correspond to 16n. According to Bilbao, 2b should be (0,0,1/2) and 4d
> should be (0,1/2,1/4) and (1/2,0,1/4).
> 
> Bilbao Crystallographic Server I4/mmm (139)
> (0,1/2,1/2)      4c
> (1/2,3/4,1/4) 16n
> (1/2,1/4,3/4)
> 
> Bilbao
> 2b  (0,0,1/2)
> 4d  (0,1/2,1/4)
>       (1/2,0,1/4)
> 
> So I guess there are some internal problems in the code or Bilbao is
> incorrect.
> 
> Best regards,
> ============================================
> Minkyu Park
> Research Institute of Basic Sciences, University of Ulsan,
> 93, Daehak-ro, Nam-gu, Ulsan, 44610 Republic of Korea
> minkyupark at ulsan.ac.kr<mailto:minkyupark at ulsan.ac.kr>
> +82-52-259-1473
> ============================================
> 
> _______________________________________________
> developers mailing list
> developers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/developers
-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Bonomea 265              Fax. 0039-040-3787249
I-34136 Trieste (Italy)             e-mail: dalcorso at sissa.it