[Pw_forum] How to correctly use Wyckoff potition and crystal_sg in QE?

[Paolo Giannozzi]

Unfortunately xcrysden doesn't know about Wyckoff positions. You may
use auxiliary code "dist.x" to verify that the structure you get is
what you want. Apart from exotic cases, you just need to provide the
space group number, and the Wyckoff sites.

Paolo

On Wed, Mar 29, 2017 at 10:39 AM, balabi <balabi at qq.com> wrote:
> Hello, I am new to quantum espresso and currently using QE 6.1
>
> I have run QE for several weeks, and have no problem running examples and
> new materials. But one thing I still can not figure out is the crystal
> structure part of pw input file.
>
> To be more specific, I don't know how to make crystal_sg work. There are few
> posts on wyckoff position and crystal_sg on this forum, but all lack some
> detail. What I need is some examples, for example simple Silicon, ZnS, etc
> that described using crystal_sg.
>
> I tried below for silicon
>
> !---------------------------
> &CONTROL
> prefix='silicon',
> calculation = 'scf' ,
> /
> &SYSTEM
> ibrav = 2,celldm(1) = 10.263,nat = 1,ntyp = 1,
> ecutwfc = 44.,ecutrho = 175.,
> ATOMIC_SPECIES
> Si   28.0855  Si.pbe-n-rrkjus_psl.1.0.0.UPF
> ATOMIC_POSITIONS crystal_sg
> Si  8a
> K_POINTS automatic
> 10 10 10   1 1 1
> !-----------------------------
>
> However, xcrysden shows error when opening this input file.
>
> Also actually, I don't quite understand wyckoff position after reading some
> web pages and how to use this database on site
> http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list?gnum=227&gor=1
> to write input file in crystal_sg form. Could somebody explain it?
>
>
>
>
>
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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