Re: [Phonopy-users] P1 symmetry but symmetry operations found
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Re: [Phonopy-users] P1 symmetry but symmetry operations found
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From: MUKESH S. <gkp...@gm...> - 2024-09-14 17:33:21
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Hi, While using phonopy to get unit-cell, it uses some threshold. Considering some small threshold, I think, there is a possibility of reduction of unit-cell. Taking inspiration from phonopy generated structure, I have created (using rotation & translation of cell) a smaller unit cell with ase and attached and its steps and reduced_POSCAR_unit, which matches with PPOSCAR file. I hope this might help. Thanks and regards Mukesh Singh Department of Physics, IIT Bombay, India On Sat, Sep 14, 2024 at 10:26 PM MUKESH SINGH <gkp...@gm...> wrote: > Hi, > > While using phonopy to get unit-cell, it uses some threshold. Considering > some small threshold, I think, there is a possibility of reduction of > unit-cell. Taking inspiration from phonopy generated structure, I have > created (using rotation & translation of cell) a smaller unit cell with ase > and attached and its steps and reduced_POSCAR_unit, which matches with > PPOSCAR file. I hope this might help. > > > Thanks and regards > Mukesh Singh > Department of Physics, > IIT Bombay, India > > On Sat, Sep 14, 2024 at 6:47 PM Antonio Cammarata via Phonopy-users < > pho...@li...> wrote: > >> Thanks for the answer. It is not still clear to me why there are >> equivalent atoms which can be mapped by symmetry operations if the only >> symmetry operation is the identity. From my understanding, if P1 is the >> space group of the unit cell provided as input, then every atom in the unit >> cell should be unique, then the unit cell is primitive and no further >> reduction is possible. >> >> Antonio >> Il 14. 09. 24 15:00, Atsushi Togo ha scritto: >> >> Hi, >> >> It is not a bug. >> >> P1 corresponds to a space group type. >> >> Space group S is expanded by cosets, >> S = \sum_i (R_i, t_i) T >> where T is the translation group and (R_i, t_i) are the coset >> representatives (the space group operations). In this way, supercell can >> not be represented in this way. >> >> The symmetry operations returned in your case are the coset >> representatives * translations in supercell. However P1 is determined from >> the primitive cell. >> >> Togo >> >> On Sat, Sep 14, 2024 at 8:29 PM Antonio Cammarata via Phonopy-users < >> pho...@li...> wrote: >> >>> Dear all >>> >>> I am using phonopy 2.28.0 with python 3.9.13 and spglib 2.3.1. I have a >>> unit cell which phonopy recognises to have space group P1, that is, with >>> just the identity as symmetry operation. However, when I call phonopy, >>> for example, to calculate the band structure, it finds space group P1 >>> but 3 symmetry operations in the supercell. In fact, if I issue the >>> command >>> >>> phonopy --symmetry -c POSCAR_unit_cell >>> >>> I get a primitive unit cell PPOSCAR which is smaller than the provided >>> unit cell, and the map of the unique atoms is provided. However, all the >>> symmetry operations associated to the atoms are represented by the >>> identity matrix. Accordingly, I expected that the primitive unit cell is >>> identical to the provided unit cell, as the recognised symmetry is P1 >>> and the only symmetry operation is the identity. Please, let me know if >>> I am missing something here. >>> >>> Please, here attached you find the unit cell to reproduce the output. >>> >>> Thanks a lot in advance for your help! >>> >>> All the best >>> >>> Antonio >>> >>> -- >>> _______________________________________________ >>> doc. Antonio Cammarata, PhD in Physics >>> Associate Professor in Applied Physics >>> Advanced Materials Group >>> Department of Control Engineering - KN:G-204 >>> Faculty of Electrical Engineering >>> Czech Technical University in Prague >>> Karlovo Náměstí, 13 >>> 121 35, Prague 2, Czech Republic >>> Phone: +420 224 35 5713 >>> Fax: +420 224 91 8646 >>> ORCID: orcid.org/0000-0002-5691-0682 >>> ResercherID: A-4883-2014 >>> _______________________________________________ >>> Phonopy-users mailing list >>> Pho...@li... >>> https://lists.sourceforge.net/lists/listinfo/phonopy-users >>> >> >> >> -- >> Atsushi Togo >> >> >> _______________________________________________ >> Phonopy-users mailing lis...@li...://lists.sourceforge.net/lists/listinfo/phonopy-users >> >> -- >> _______________________________________________ >> doc. Antonio Cammarata, PhD in Physics >> Associate Professor in Applied Physics >> Advanced Materials Group >> Department of Control Engineering - KN:G-204 >> Faculty of Electrical Engineering >> Czech Technical University in Prague >> Karlovo Náměstí, 13 >> 121 35, Prague 2, Czech Republic >> Phone: +420 224 35 5713 >> Fax: +420 224 91 8646 >> ORCID: orcid.org/0000-0002-5691-0682 >> ResercherID: A-4883-2014 >> >> _______________________________________________ >> Phonopy-users mailing list >> Pho...@li... >> https://lists.sourceforge.net/lists/listinfo/phonopy-users >> > > > -- > Thanks and regards > Mukesh Singh > Research Scholar > Department of Physics, > IIT BOMBAY(400076), India. > Website: Google Sites > <https://sites.google.com/view/mukeshphy/home?authuser=0> > Publications link: Google Scholar > <https://scholar.google.co.in/citations?user=Lfi6CDsAAAAJ&hl=en> > -- Thanks and regards Mukesh Singh Research Scholar Department of Physics, IIT BOMBAY(400076), India. Website: Google Sites <https://sites.google.com/view/mukeshphy/home?authuser=0> Publications link: Google Scholar <https://scholar.google.co.in/citations?user=Lfi6CDsAAAAJ&hl=en> |
