[QE-users] How does pw.x make the cell choice for space group No.12 with unique axis b ?

[Paolo Giannozzi]

The Bravais lattice for the case of unique axis 'b' should be  the one
corresponding to case ibrav=-13, as described in the documentation

Paolo

On Tue, Dec 15, 2020 at 9:30 AM 连云龙 <lianyl at ihep.ac.cn> wrote:

> Dear QE experts,
>
>
> I find it confusing in the description Wyckoff position specifications in
> the card ATOMIC_POSITIONS.
>
> https://www.quantum-espresso.org/Doc/INPUT_PW.html
>
>
> For space group No.12 under the convention unique axis b, there are three
> cell choices. The Wyckoff position 4i has different forms for the three
> choices, namely (according to ITA)
>
> UNIQUE AXIS b, CELL CHOICE 1
>
> 4i  x,0,z  ;  x+1/2,1/2,z  ;  xb,0,zb  ;  xb+1/2,1/2,zb
>
> UNIQUE AXIS b, CELL CHOICE 2
>
> 4i  x,0,z  ;  x,1/2,z+1/2  ;  xb,0,zb  ;  xb,1/2,zb+1/2
>
> UNIQUE AXIS b, CELL CHOICE 3
>
> 4i  x,0,z  ;  x+1/2,1/2,z+1/2  ;  xb,0,zb  ;  xb+1/2,1/2,zb+1/2
>
> (xb means x-bar)
>
>
> If I am to write the ATOMIC_POSITIONS card, how should I specify the
> parameters x and z? How do I know that pw.x takes CELL CHOICE 1/2/3 ?
>
>
> Thank you for your help.
>
>
> Best regards,
>
> Yunlong Lian
>
> --
> Yunlong LIAN ORCID : https://orcid.org/0000-0002-9474-2181 CSNS, Dongguan
> Neutron Science Center Dongguan, Guangdong, P. R. China 连云龙 中国散裂中子源 中子科学部
> A1-629 (内线 303) 中国广东省东莞市
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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