[Pw_forum] Symmetry recognition

[Louis Fry-Bouriaux]

Hi Pascal,


     When I first started using QE 6.0 not long ago I had trouble using crystal_sg, I suppose you have the Wyckoff positions of your atoms. What I did was use the VESTA program which allows you to input Wyckoff positions and it will correctly generate the cell as long as other options are correct. I then exported to an xyz file and converted the coordinates in angstroms to internal crystal coordinates ('crystal' option) using:

https://en.wikipedia.org/wiki/Fractional_coordinates

Fractional coordinates - Wikipedia<https://en.wikipedia.org/wiki/Fractional_coordinates>
en.wikipedia.org
In crystallography, a fractional coordinate system is a coordinate system in which the edges of the unit cell are used as the basic vectors to describe the positions ...


Which worked perfectly for me. This is easily done with a Python script or something similar!


Kindest regards,

Louis

________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Pascal Boulet <pascal.boulet at univ-amu.fr>
Sent: 23 February 2017 07:56:16
To: PWSCF Forum
Subject: [Pw_forum] Symmetry recognition

Dear all,

I am running a structural optimization with QE 6.0. The structure is orthorhombic, ibrav=8, with 8 symmetry elements. The first run did not converge so I have to restart it. But as I restart it, the number of symmetry is now 4, there is a descent of symmetry. I shall say that I use the space_group option with COORDINATES crystal_sg. But the problem remains if I put all the coordinates (unsurprisingly).

Is there a reason for this, and can I avoid this?

Thank you
Best regards
Pascal

-
Pascal Boulet - MCF HDR, Resp. L2 MPCI - DEPARTEMENT CHIMIE
Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 Marseille
Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50
Site : http://madirel.univ-amu.fr/pages_web_BOULET_PASCAL/annuaire<http://amu.fr/pages_web_BOULET_PASCAL/annuaire> - Email : pascal.boulet at univ-amu.fr<mailto:pascal.boulet at univ-amu.fr>




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