[Phonopy-users] P1 symmetry but symmetry operations found

[Antonio C. <cam...@fe...>]

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